Low traction/energy efficient liquid crystal base stocks

ABSTRACT

A method for improving wear control, while maintaining or improving energy efficiency, in an engine or other mechanical component lubricated with a lubricating oil, by using as the lubricating oil a formulated oil. The formulated oil includes at least one lubricating oil base stock having one or more liquid crystals represented by the formula: 
       R1-(A) m -Y—(B) n —R2
 
     wherein R1 and R2 are the same or different and are a substituted or unsubstituted, hydrocarbon, alkoxy or alkylthio group having from 2 to 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH2-CH2-, —CH═CH—, —OCOO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO2-, —CH2O—, —OCH2O—, —NO—, —ONO2, or —C≡N; and m and n are independently 0, 1, 2 or 3. The lubricating oil base stock has a kinematic viscosity of 2 cSt to 200 cSt at 40° C., and 1 cSt to 25 cSt at 100° C. Also, this disclosure relates to low traction/energy efficient liquid crystal base stocks containing liquid crystals.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 62/611,072, filed on Dec. 28, 2017, the entire contents of which are incorporated herein by reference.

In addition, this application also claims the benefit of related U.S. Provisional Application Nos. 62/611,057 and 62/611,081, both filed on Dec. 28, 2017, the entire contents of which are also incorporated herein by reference.

FIELD

This disclosure relates to low traction/energy efficient liquid crystal base stocks, in particular, low traction/energy efficient liquid crystal base stocks containing liquid crystals and discotic liquid crystals that can approach super lubricity with friction coefficients of ˜0.01. The base stocks are useful in lubricating oils for internal combustion engines and other mechanical components lubricated with a lubricating oil. Also, this disclosure relates to method for improving wear control, while maintaining or improving energy efficiency, in an engine or other mechanical component lubricated with a lubricating oil, by using a lubricating oil containing at least one lubricating oil base stock having one or more nematic, smectic or discotic liquid crystals.

BACKGROUND

Formulators are turning to lower and lower viscosity oils to meet the energy efficiency demands. These systems pose issues with controlling wear, forming fluid films, and bearing load and in turn rely heavily on tribofilm-forming additives to keep parts separated. Often these film-forming additives have the downside of increasing boundary friction due to roughness of the film (frequent with molybdenum- and zinc-based tribofilm forming additives).

Energy efficiency demands challenge lubricant formulators to formulate fluids with low friction and traction. Low traction lubricants are normally comprised of heteroatom-containing base oils such as PAGs (polyalkylene glycols), which are hydrocarbon imiscibile and require special additive systems, or they may employ low viscosity base oils with highly-formulated surfactant packages to circumvent potential damage from parts touching due to inadequate film formation.

Further, the low traction base oils (including PAGs) are often incompatible with hydrocarbon fluids and also may pose issues for compatibility with some seals making them undesirable for numerous applications.

A major challenge in engine oil formulation is the development of alternate pathways to low traction without decreasing bulk viscosity or dealing with additive compatibility issues.

SUMMARY

In accordance with this disclosure, liquid crystal base oils are provided that offer a route to improve lubricant energy efficiency without reducing load-bearing capability. As compared to simple hydrocarbon fluids, the viscosity of the liquid crystal base oil does not need to be lowered to achieve improved traction. Further, a film thickness profile in EHL shows thicker-than-expected films at slow speeds and thinner films at high speeds. In this manner, metal-metal contact may be avoided for longer at slow speeds, and hydrodynamic losses are lesser at higher speeds compared to simple fluids of similar viscosity.

Also, in accordance with this disclosure, the use of low traction base stock comprised of liquid crystals such as S2 or analogs with differing R group side chains or differing core structure still containing two rings, at least one aromatic, with or without additional additives or base stocks present, to give lower traction compared to non-liquid crystal hydrocarbon fluids of the same viscosities. The liquid crystal lubricants exhibit unprecedented low traction levels from hydrocarbon-only fluids.

This disclosure relates in part to a lubricating oil base stock comprising one or more liquid crystals. The one or more liquid crystals are represented by the formula:

R1-(A)_(m)-Y—(B)_(n)—R2

wherein R1 and R2 are the same or different and are a substituted or unsubstituted, hydrocarbon, alkoxy, or alkythio group having from about 2 to about 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH2-CH2-, —CH═CH—, —OCOO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO2-, —CH2O—, —OCH2O—, —NO—, —ONO2, or —C≡N; and m and n are independently 0, 1, 2 or 3. The lubricating oil base stock has a kinematic viscosity of about 2 cSt to about 200 cSt at 40° C., as determined according to ASTM D445, and a kinematic viscosity of about 1 cSt to about 25 cSt at 100° C., as determined according to ASTM D445.

This disclosure also relates in part to a method for improving wear control, while maintaining or improving energy efficiency, in an engine or other mechanical component lubricated with a lubricating oil, by using as the lubricating oil a formulated oil. The formulated oil has a composition comprising at least one lubricating oil base stock. The at least one lubricating oil base stock comprises one or more liquid crystals. The one or more liquid crystals are represented by the formula:

R1-(A)_(m)-Y—(B)_(n)—R2

wherein R1 and R2 are the same or different and are a substituted or unsubstituted, hydrocarbon, alkoxy, or alkythio group having from about 2 to about 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH2-CH2-, —CH═CH—, —OCOO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO2-, —CH2O—, —OCH2O—, —NO—, —ONO2, or —C≡N; and m and n are independently 0, 1, 2 or 3. The lubricating oil base stock has a kinematic viscosity of about 2 cSt to about 200 cSt at 40° C., as determined according to ASTM D445, and a kinematic viscosity of about 1 cSt to about 25 cSt at 100° C., as determined according to ASTM D445. Wear control is improved and energy efficiency is maintained or improved as compared to wear control and energy efficiency achieved using a lubricating oil containing a lubricating oil base stock other than the lubricating oil base stock comprising one or more liquid crystals.

It has been surprisingly found that, in accordance with this disclosure, improvements in wear control in an engine or other mechanical component lubricated with a lubricating oil are obtained, when the lubricating oil contains at least one lubricating oil base stock comprised of one or more liquid crystals, and optionally a viscosity modifier (e.g., a polymer thickening agent).

In particular, it has been surprisingly found that, in accordance with this disclosure, with respect to the lubricating oil base stock comprised of one or more liquid crystals, (i) in friction coefficient measurements of the lubricating oil base stock by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 100° C., and a pressure of 1 GPa, the friction coefficient is less than about 0.02; (ii) in friction coefficient measurements of the lubricating oil base stock by a mini-traction machine (MTM) at a 30% slide-to-roll ratio (SRR), a temperature of 80° C., and over a pressure of 0.6-1.4 GPa, the friction coefficient is less than about 0.02; (iii) in friction coefficient measurements of the lubricating oil base stock by a mini-traction machine (MTM) at a 30% slide-to-roll ratio (SRR), a pressure of 1 GPa, and over a temperature of 0° C.-150° C., the friction coefficient is less than about 0.025; and (iv) in elastohydrodynamic lubrication (EHL) film measurements of the lubricating oil base stock over a 10-1000 mm/s rolling speed using a mini-traction machine (MTM), at a temperature of 40° C. or 100° C., the EHL film thickness is greater than about 8 nm.

Also, in particular, it has been surprisingly found that, in accordance with this disclosure, with respect to bimodal blends of the lubricating oil base stock comprised of one or more liquid crystals, and a viscosity modifier (e.g., a polymer thickening agent), (i) in friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 40° C., and a pressure of 0.75 GPa, the friction coefficient is less than about 0.02; (ii) in friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 40° C., and a pressure of 1.25 GPa, the friction coefficient is less than about 0.025; (iii) in friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 100° C., and a pressure of 0.75 GPa, the friction coefficient is less than about 0.01; and (iv) in friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 100° C., and a pressure of 1.25 GPa, the friction coefficient is less than about 0.02.

Other objects and advantages of the present disclosure will become apparent from the detailed description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows illustrative liquid crystal base oils in accordance with the Examples.

FIG. 2 shows illustrative liquid crystal base oils, including viscosity and mesophases, in accordance with the Examples.

FIG. 3 graphically depicts friction coefficient over 0-100% slide-to-roll ratio (SRR), a temperature of 100° C., and a pressure of 1 GPa, on MTM traction test for a low viscosity PAG (4 cSt at 100° C., squares), two PAO fluids (8 cSt, circles, and 4 cSt, triangles) and four liquid crystal materials: D1 (diamonds), S2 (short dash line), S8 (continuous line), S11 (long dash line), in accordance with the Examples.

FIG. 4 shows average traction coefficient for low viscosity PAG, two PAO fluids, and four liquid crystal materials, over 0-100% slide-to-roll ratio (SRR) compared to PAO4, in accordance with the Examples.

FIG. 5 graphically depicts friction coefficient versus pressure at slide-to-roll ratio (SRR) 30% and 80° C. in MTM traction test for liquid crystals S2 and 8CB as well as PAO 3.6, in accordance with the Examples.

FIG. 6 graphically depicts friction coefficient versus temperature at slide-to-roll ratio (SRR) 30% and 1.0 GPa Hertzian pressure for liquid crystals S2 and 8CB and conventional fluid PAO 3.6, in accordance with the Examples.

FIG. 7 graphically depicts elastohydrodynamic lubrication (EHL) film thickness versus rolling speed (mm/s) for S2 and PAO4 at two temperatures (i.e., 40° C. and 100° C.), in accordance with the Examples.

FIG. 8 shows bimodal blends prepared from a high viscosity copolymer, PAO2, PAO4, S2, and an additive package, in accordance with the Examples.

FIG. 9 graphically depicts friction coefficient over 0-100% slide-to-roll ratio (SRR) in MTM traction for bimodal blends of similar viscosity (˜460 cSt at 40° C.), in accordance with the Examples. The bimodal blends include PAO2 (squares), PAO4 (triangles) S2 (circles) and a gear and bearing oil (diamonds).

FIG. 10 graphically depicts friction coefficient over 0-100% slide-to-roll ratio (SRR) in MTM traction for bimodal blends of similar viscosity (˜460 cSt at 40° C.), in accordance with the Examples. The bimodal blends include PAO2 (squares), PAO4 (triangles) S2 (circles) and a gear and bearing oil (diamonds).

FIG. 11 graphically depicts friction coefficient over 0-100% slide-to-roll ratio (SRR) in MTM traction for bimodal blends of similar viscosity (˜460 cSt at 40° C.), in accordance with the Examples. The bimodal blends include PAO2 (squares), PAO4 (triangles) S2 (circles) and a gear and bearing oil (diamonds).

FIG. 12 graphically depicts friction coefficient over 0-100% slide-to-roll ratio (SRR) in MTM traction for bimodal blends of similar viscosity (˜460 cSt at 40° C.), in accordance with the Examples. The bimodal blends include PAO2 (squares), PAO4 (triangles) S2 (circles) and a gear and bearing oil (diamonds).

FIG. 13 graphically depicts the effect of gradual addition of liquid crystal S2 into 4 cSt PAO on friction reduction over 0-100% slide-to-roll ratio (SRR) at fixed pressure of 0.75 GPa and various temperatures from 40° C. to 140° C. Gradual reduction of traction coefficient is clearly associated with the increase of liquid crystal S2 concentration.

FIG. 14 graphically depicts the effect of gradual addition of liquid crystal S2 into 4 cSt PAO on friction reduction over 0-100% slide-to-roll ratio (SRR) at fixed temperature of 80° C. and various pressures from 0.75 GPa to 1.25 GPa. Gradual reduction of traction coefficient is clearly associated with the increase of liquid crystal S2 concentration.

DETAILED DESCRIPTION Definitions

“About” or “approximately.” All numerical values within the detailed description and the claims herein are modified by “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.

“Liquid crystal” fluids mean highly anisotropic fluids that exist between the boundaries of the solid and conventional isotropic liquid phase. The phase is a result of long-range orientational ordering among constituent molecules that occurs within certain ranges or temperature in melts and solutions of many organic compounds. The various liquid crystal phases may be characterized by the type of ordering. Among these are namely nematic, smectic or discotic phases.

“Smectic liquid crystals” refer to hydrocarbon molecules that are arranged in layers, with the long molecular axes approximately perpendicular to the laminar planes. The only long range order extends along this axis, with the result that individual layers can slip over each other (soap-like in nature). A smectic phase of a liquid crystal can possess two directions of order including one along the axis of molecular orientation, and the other along the traverse axis where molecules show layering.

“Major amount” as it relates to components included within the lubricating oils of the specification and the claims means greater than or equal to 50 wt. %, or greater than or equal to 60 wt. %, or greater than or equal to 70 wt. %, or greater than or equal to 80 wt. %, or greater than or equal to 90 wt. % based on the total weight of the lubricating oil.

“Minor amount” as it relates to components included within the lubricating oils of the specification and the claims means less than 50 wt. %, or less than or equal to 40 wt. %, or less than or equal to 30 wt. %, or greater than or equal to 20 wt. %, or less than or equal to 10 wt. %, or less than or equal to 5 wt. %, or less than or equal to 2 wt. %, or less than or equal to 1 wt. %, based on the total weight of the lubricating oil.

“Essentially free” as it relates to components included within the lubricating oils of the specification and the claims means that the particular component is at 0 weight % within the lubricating oil, or alternatively is at impurity type levels within the lubricating oil (less than 100 ppm, or less than 20 ppm, or less than 10 ppm, or less than 1 ppm).

“Flat viscosity” temperature performance as it relates to the lubricant base stocks and lubricating oils disclosed herein mean that the viscosity does not vary as a function of temperature over a temperature range from 20 to 100 deg. C.

“Other lubricating oil additives” as used in the specification and the claims means other lubricating oil additives that are not specifically recited in the particular section of the specification or the claims. For example, other lubricating oil additives may include, but are not limited to, antioxidants, detergents, dispersants, antiwear additives, corrosion inhibitors, viscosity modifiers, metal passivators, pour point depressants, seal compatibility agents, antifoam agents, extreme pressure agents, friction modifiers and combinations thereof.

“Other mechanical component” as used in the specification and the claims means an electric vehicle component, a hybrid vehicle component, a power train, a driveline, a transmission, a gear, a gear train, a gear set, a compressor, a pump, a hydraulic system, a bearing, a bushing, a turbine, a piston, a piston ring, a cylinder liner, a cylinder, a cam, a tappet, a lifter, a gear, a valve, or a bearing including a journal, a roller, a tapered, a needle, and a ball bearing.

“Hydrocarbon” refers to a compound consisting of carbon atoms and hydrogen atoms.

“Alkane” refers to a hydrocarbon that is completely saturated. An alkane can be linear, branched, cyclic, or substituted cyclic.

“Olefin” refers to a non-aromatic hydrocarbon comprising one or more carbon-carbon double bond in the molecular structure thereof.

“Mono-olefin” refers to an olefin comprising a single carbon-carbon double bond.

“Cn” group or compound refers to a group or a compound comprising carbon atoms at total number thereof of n. Thus, “Cm-Cn” group or compound refers to a group or compound comprising carbon atoms at a total number thereof in the range from m to n. Thus, a C1-C50 alkyl group refers to an alkyl group comprising carbon atoms at a total number thereof in the range from 1 to 50.

“Carbon backbone” refers to the longest straight carbon chain in the molecule of the compound or the group in question. “Branch” refer to any substituted or unsubstituted hydrocarbyl group connected to the carbon backbone. A carbon atom on the carbon backbone connected to a branch is called a “branched carbon.”

“SAE” refers to SAE International, formerly known as Society of Automotive Engineers, which is a professional organization that sets standards for internal combustion engine lubricating oils.

“SAE J300” refers to the viscosity grade classification system of engine lubricating oils established by SAE, which defines the limits of the classifications in rheological terms only.

“Base stock” or “base oil” interchangeably refers to an oil that can be used as a component of lubricating oils, heat transfer oils, hydraulic oils, grease products, and the like.

“Lubricating oil” or “lubricant” interchangeably refers to a substance that can be introduced between two or more surfaces to reduce the level of friction between two adjacent surfaces moving relative to each other. A lubricant base stock is a material, typically a fluid at various levels of viscosity at the operating temperature of the lubricant, used to formulate a lubricant by admixing with other components. Non-limiting examples of base stocks suitable in lubricants include API Group I, Group II, Group III, Group IV, and Group V base stocks. PAOs, particularly hydrogenated PAOs, have recently found wide use in lubricants as a Group IV base stock, and are particularly preferred. If one base stock is designated as a primary base stock in the lubricant, additional base stocks may be called a co-base stock.

All kinematic viscosity values in this disclosure are as determined pursuant to ASTM D445. Kinematic viscosity at 100° C. is reported herein as KV100, and kinematic viscosity at 40° C. is reported herein as KV40. Unit of all KV100 and KV40 values herein is cSt unless otherwise specified.

All viscosity index (“VI”) values in this disclosure are as determined pursuant to ASTM D2270.

All Noack volatility (“NV”) values in this disclosure are as determined pursuant to ASTM D5800 unless specified otherwise. Unit of all NV values is wt %, unless otherwise specified.

All pour point values in this disclosure are as determined pursuant to ASTM D5950 or D97.

All CCS viscosity (“CCSV”) values in this disclosure are as determined pursuant to ASTM 5293. Unit of all CCSV values herein is millipascal second (mPa·s), which is equivalent to centipoise), unless specified otherwise. All CCSV values are measured at a temperature of interest to the lubricating oil formulation or oil composition in question. Thus, for the purpose of designing and fabricating engine oil formulations, the temperature of interest is the temperature at which the SAE J300 imposes a minimal CCSV.

All percentages in describing chemical compositions herein are by weight unless specified otherwise. “Wt. %” means percent by weight.

It has now been found that improved wear control can be attained through the use of lubricants containing liquid crystal base oils. The liquid crystal base oils offer a route to improve lubricant energy efficiency without reducing load-bearing capability. As compared to simple hydrocarbon fluids, the viscosity of the liquid crystal base oil does not need to be lowered to achieve improved traction. Further, a film thickness profile in EHL shows thicker-than-expected films at slow speeds and thinner films at high speeds. In this manner, metal-metal contact may be avoided for longer at slow speeds, and hydrodynamic losses are lesser at higher speeds compared to simple fluids of similar viscosity.

Also, for the lubricants containing liquid crystal base stocks of this disclosure, it has been found that, in friction coefficient measurements of the lubricating oil base stock by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 100° C., and a pressure of 1 GPa, the friction coefficient is less than about 0.02.

Further, for the lubricants containing liquid crystal base stocks of this disclosure, it has been found that, in friction coefficient measurements of the lubricating oil base stock by a mini-traction machine (MTM) at a 30% slide-to-roll ratio (SRR), a temperature of 80° C., and over a pressure of 0.6-1.4 GPa, the friction coefficient is less than about 0.02.

Yet further, for the lubricants containing liquid crystal base stocks of this disclosure, it has been found that, in friction coefficient measurements of the lubricating oil base stock by a mini-traction machine (MTM) at a 30% slide-to-roll ratio (SRR), a pressure of 1 GPa, and over a temperature of 0° C.-150° C., the friction coefficient is less than about 0.025.

Still further, for the lubricants containing liquid crystal base stocks of this disclosure, it has been found that, in elastohydrodynamic lubrication (EHL) film measurements of the lubricating oil base stock over a 10-1000 mm/s rolling speed using a mini-traction machine (MTM), at a temperature of 40° C. or 100° C., the EHL film thickness is greater than about 8 nm.

In an embodiment, the lubricants containing liquid crystal base oils of this disclosure, can be blended with one or more additives, e.g., a viscosity modifier (e.g., a polymer thickening agent), to form bimodal blends.

For the bimodal blends containing a liquid crystal base oil and a viscosity modifier (e.g., a polymer thickening agent) in accordance with this disclosure, it has been found that, in friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 40° C., and a pressure of 0.75 GPa, the friction coefficient is less than about 0.02.

Also, for the bimodal blends containing a liquid crystal base oil and a viscosity modifier (e.g., a polymer thickening agent) in accordance with this disclosure, it has been found that, in friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 40° C., and a pressure of 1.25 GPa, the friction coefficient is less than about 0.025.

Further, for the bimodal blends containing a liquid crystal base oil and a viscosity modifier (e.g., a polymer thickening agent) in accordance with this disclosure, it has been found that, in friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 100° C., and a pressure of 0.75 GPa, the friction coefficient is less than about 0.01.

Yet further, for the bimodal blends containing a liquid crystal base oil and a viscosity modifier (e.g., a polymer thickening agent) in accordance with this disclosure, it has been found that, in friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 100° C., and a pressure of 1.25 GPa, the friction coefficient is less than about 0.02.

The present disclosure provides lubricant compositions with excellent antiwear properties. Antiwear additives are generally required for reducing wear in operating equipment where two solid surfaces engage in contact. In the absence of antiwear chemistry, the surfaces can rub together causing material loss on one or both surfaces which can eventually lead to equipment malfunction and failure. Antiwear additives can produce a protective surface layer which reduces wear and material loss. Most commonly the materials of interest are metals such as steel and other iron-containing alloys. However, other materials such as ceramics, polymer coatings, diamond-like carbon, corresponding composites, and the like can also be used to produce durable surfaces in modern equipment. The lubricant compositions of this disclosure can provide antiwear properties to such surfaces.

The lubricant compositions of this disclosure provide advantaged wear, including advantaged wear and friction, performance in the lubrication of internal combustion engines, power trains, drivelines, transmissions, gears, gear trains, valve trains, gear sets, and the like.

Also, the lubricant compositions of this disclosure provide advantaged wear, including advantaged wear and friction, performance in the lubrication of mechanical components, which can include, for example, pistons, piston rings, cylinder liners, cylinders, cams, tappets, lifters, bearings (journal, roller, tapered, needle, ball, and the like), gears, valves, and the like.

Further, the lubricant compositions of this disclosure provide advantaged wear, including advantaged wear and friction, performance as a component in lubricant compositions, which can include, for example, lubricating liquids, semi-solids, solids, greases, dispersions, suspensions, material concentrates, additive concentrates, and the like.

Also, the lubricant compositions of this disclosure provide advantaged wear, including advantaged wear and friction, performance in spark-ignition internal combustion engines, compression-ignition internal combustion engines, mixed-ignition (spark-assisted and compression) internal combustion engines, and the like, through the generation of tribofilms under loading/temperature conditions relevant to light-duty passenger vehicle operation.

Further, the lubricant compositions of this disclosure provide advantaged wear, including advantaged wear and friction, performance through the generation of tribofilms on lubricated surfaces that include, for example, the following: metals, metal alloys, non-metals, non-metal alloys, mixed carbon-metal composites and alloys, mixed carbon-nonmetal composites and alloys, ferrous metals, ferrous composites and alloys, non-ferrous metals, non-ferrous composites and alloys, titanium, titanium composites and alloys, aluminum, aluminum composites and alloys, magnesium, magnesium composites and alloys, ion-implanted metals and alloys, plasma modified surfaces; surface modified materials; coatings; mono-layer, multi-layer, and gradient layered coatings; honed surfaces; polished surfaces; etched surfaces; textured surfaces; micro and nano structures on textured surfaces; super-finished surfaces; diamond-like carbon (DLC), DLC with high-hydrogen content, DLC with moderate hydrogen content, DLC with low-hydrogen content, DLC with near-zero hydrogen content, DLC composites, DLC-metal compositions and composites, DLC-nonmetal compositions and composites; ceramics, ceramic oxides, ceramic nitrides, FeN, CrN, ceramic carbides, mixed ceramic compositions, and the like; polymers, thermoplastic polymers, engineered polymers, polymer blends, polymer alloys, polymer composites; materials compositions and composites containing dry lubricants, that include, for example, graphite, carbon, molybdenum, molybdenum disulfide, polytetrafluoroethylene, polyperfluoropropylene, polyperfluoroalkylethers, and the like.

Lubricating Oil Base Stocks Containing Liquid Crystals

The low traction base stocks of this disclosure are comprised of liquid crystals such as S2 or analogs with differing R group side chains or differing core structure still containing two rings, at least one aromatic, with or without additional additives or base stocks present, to give lower traction compared to non-liquid crystal hydrocarbon fluids of the same viscosities. The liquid crystals do not contain any heteroatoms.

The lubricating oil base stocks of this disclosure comprise one or more liquid crystals. The one or more liquid crystals are represented by the formula:

R1-(A)_(m)-Y—(B)_(n)—R2

wherein R1 and R2 are the same or different and are a substituted or unsubstituted, hydrocarbon, alkoxy, or alkythio group having from about 2 to about 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH2-CH2-, —CH═CH—, —OCOO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO2-, —CH2O—, —OCH2O—, —NO—, —ONO2, or —C≡N; and m and n are independently 0, 1, 2 or 3. The lubricating oil base stock has a kinematic viscosity of about 2 cSt to about 200 cSt at 40° C., as determined according to ASTM D445, and a kinematic viscosity of about 1 cSt to about 25 cSt at 100° C., as determined according to ASTM D445.

Illustrative liquid crystals useful in this disclosure include, for example, those represented by the formula:

In particular, illustrative liquid crystals useful in this disclosure include, for example, 4′-n-octyl-4-cyano-biphenyl, 4-(trans-4-heptylcyclohexyl)-pentylbenzene, 4-(trans-4-heptylcyclohexyl)-propylbenzene, 4-(trans-4-propylcyclohexyl)-ethylbenzene, and mixtures thereof.

Other liquid crystals useful in this disclosure additionally include, 4-pentylphenyl, 4-methylbenzoate, 4-pentylphenyl 4-ethylbenzoate, 4-pentylphenyl 4-propylbenzoate, 4-pentylphenyl 4-butylbenzoate, 4-pentylphenyl 4-(octyloxy)benzoate, 4-pentylphenyl 4-methoxybenzoate, 4-pentylphenyl 4-ethoxybenzoate, 4-pentylphenyl 4-propoxybenzoate, 4-pentylphenyl 4-butoxybenzoate, 4-pentylphenyl 4-pentoxybenzoate, and mixtures thereof.

The liquid crystal materials of this disclosure access a state of matter that is both fluid and anisotropic in nature—essentially these materials are not solids, which possess a highly ordered crystalline structure and lack ability of translation of molecules in any direction, and they are not liquids, which are characterized by their lack of order but intermolecular forces that overcome kinetic energy, keeping them in a condensed phase. Instead liquid crystals can be considered “partly ordered” in that in some direction(s) they may appear ordered, and in others they may appear disordered. These materials are therefore anisotropic in nature, and the amount of ordering seen depends on from which angle they are viewed. A smectic phase of a liquid crystal can possess two directions of order including one along the axis of molecular orientation, and the other along the traverse axis where molecules show layering.

Accordingly, as used herein, “liquid crystal” means highly anisotropic fluids that exist between the boundaries of the solid and conventional isotropic liquid phase. The phase is a result of long-range orientational ordering among constituent molecules that occurs within certain ranges or temperature in melts and solutions of many organic compounds.

As used herein, “smectic liquid crystals” refers to hydrocarbon molecules that are arranged in layers, with the long molecular axes approximately perpendicular to the laminar planes. The only long range order extends along this axis, with the result that individual layers can slip over each other (soap-like in nature). A smectic phase of a liquid crystal can possess two directions of order including one along the axis of molecular orientation, and the other along the traverse axis where molecules show layering.

The liquid crystal base oils of this disclosure conveniently have a kinematic viscosity, according to ASTM standards, of about 2 cSt to about 200 cSt (or mm²/s) at 40° C. and preferably of about 2.5 cSt to about 100 cSt (or mm²/s) at 40° C., often more preferably from about 2.5 cSt to about 500 cSt at 40° C. Also, the liquid crystal base oil conveniently has a kinematic viscosity, according to ASTM standards, of about 1 cSt to about 25 cSt (or mm²/s) at 100° C. and preferably of about 2.5 cSt to about 20 cSt (or mm²/s) at 100° C., often more preferably from about 2.5 cSt to about 15 cSt at 100° C.

Mixtures of liquid crystal base oils may be used if desired. Bi-modal, tri-modal, and additional combinations of mixtures of liquid crystal base oils and optional Group I, II, III, IV, and/or V base stocks may be used if desired. With mixtures of liquid crystal base oils and Group I, II, III, IV, and/or V base stocks, the liquid crystal base oil is present is an amount ranging from about 5 to about 99 weight percent or from about 10 to about 95 weight percent, preferably from about 50 to about 99 weight percent or from about 70 to about 95 weight percent, and more preferably from about 85 to about 95 weight percent, based on the total weight of the composition. Preferably, with mixtures of liquid crystal base oils and Group I, II, III, IV, and/or V base stocks, the liquid crystal base oil is present is an amount ranging from about 50 to about 99 weight percent or from about 55 to about 95 weight percent, preferably from about 60 to about 99 weight percent or from about 70 to about 95 weight percent, and more preferably from about 85 to about 95 weight percent, based on the total weight of the composition.

The liquid crystal base oil typically is present in an amount ranging from about 5 to about 99 weight percent or from about 10 to about 95 weight percent, preferably from about 50 to about 99 weight percent or from about 70 to about 95 weight percent, and more preferably from about 85 to about 95 weight percent, based on the total weight of the composition.

Preferably, the liquid crystal base oil constitutes the major component of the engine, or other mechanical component, oil lubricant composition of the present disclosure and typically is present in an amount ranging from greater than about 50 to about 99 weight percent or from about 55 to about 95 weight percent, preferably from about 60 to about 99 weight percent or from about 70 to about 95 weight percent, and more preferably from about 85 to about 95 weight percent, based on the total weight of the composition.

Optional Lubricating Oil Base Stocks

A wide range of optional lubricating base oils is known in the art. Optional lubricating base oils that are useful in the present disclosure are natural oils, mineral oils and synthetic oils, and unconventional oils (or mixtures thereof) can be used unrefined, refined, or rerefined (the latter is also known as reclaimed or reprocessed oil). Unrefined oils are those obtained directly from a natural or synthetic source and used without added purification. These include shale oil obtained directly from retorting operations, petroleum oil obtained directly from primary distillation, and ester oil obtained directly from an esterification process. Refined oils are similar to the oils discussed for unrefined oils except refined oils are subjected to one or more purification steps to improve at least one lubricating oil property. One skilled in the art is familiar with many purification processes. These processes include solvent extraction, secondary distillation, acid extraction, base extraction, filtration, and percolation. Rerefined oils are obtained by processes analogous to refined oils but using an oil that has been previously used as a feed stock.

Groups I, II, III, IV and V are broad base oil stock categories developed and defined by the American Petroleum Institute (API Publication 1509; www.API.org) to create guidelines for lubricant base oils. Group I base stocks have a viscosity index of between about 80 to 120 and contain greater than about 0.03% sulfur and/or less than about 90% saturates. Group II base stocks have a viscosity index of between about 80 to 120, and contain less than or equal to about 0.03% sulfur and greater than or equal to about 90% saturates. Group III stocks have a viscosity index greater than about 120 and contain less than or equal to about 0.03% sulfur and greater than about 90% saturates. Group IV includes polyalphaolefins (PAO). Group V base stock includes base stocks not included in Groups I-IV. The table below summarizes properties of each of these five groups.

Base Oil Properties Saturates Sulfur Viscosity Index Group I <90 and/or  >0.03% and ≥80 and <120 Group II ≥90 and ≤0.03% and ≥80 and <120 Group III ≥90 and ≤0.03% and ≥120 Group IV polyalphaolefins (PAO) Group V All other base oil stocks not included in Groups I, II, III or IV

Natural oils include animal oils, vegetable oils (castor oil and lard oil, for example), and mineral oils. Animal and vegetable oils possessing favorable thermal oxidative stability can be used. Of the natural oils, mineral oils are preferred. Mineral oils vary widely as to their crude source, for example, as to whether they are paraffinic, naphthenic, or mixed paraffinic-naphthenic. Oils derived from coal or shale are also useful. Natural oils vary also as to the method used for their production and purification, for example, their distillation range and whether they are straight run or cracked, hydrorefined, or solvent extracted.

Group II and/or Group III hydroprocessed or hydrocracked base stocks are also well known base stock oils.

Synthetic oils include hydrocarbon oil. Hydrocarbon oils include oils such as polymerized and interpolymerized olefins (polybutylenes, polypropylenes, propylene isobutylene copolymers, ethylene-olefin copolymers, and ethylene-alphaolefin copolymers, for example). Polyalphaolefin (PAO) oil base stocks are commonly used synthetic hydrocarbon oil. By way of example, PAOs derived from C₈, C₁₀, C₁₂, C₁₄ olefins or mixtures thereof may be utilized. See U.S. Pat. Nos. 4,956,122; 4,827,064; and 4,827,073.

The number average molecular weights of the PAOs, which are known materials and generally available on a major commercial scale from suppliers such as ExxonMobil Chemical Company, Chevron Phillips Chemical Company, BP, and others, typically vary from about 250 to about 3,000, although PAO's may be made in viscosities up to about 150 cSt (100° C.). The PAOs are typically comprised of relatively low molecular weight hydrogenated polymers or oligomers of alphaolefins which include, but are not limited to, C₂ to about C₃₂ alphaolefins with the C₈ to about C₁₆ alphaolefins, such as 1-octene, 1-decene, 1-dodecene and the like, being preferred. The preferred polyalphaolefins are poly-1-octene, poly-1-decene and poly-1-dodecene and mixtures thereof and mixed olefin-derived polyolefins. However, the dimers of higher olefins in the range of C₁₂ to C₁₈ may be used to provide low viscosity base stocks of acceptably low volatility. Depending on the viscosity grade and the starting oligomer, the PAOs may be predominantly dimers, trimers and tetramers of the starting olefins, with minor amounts of the lower and/or higher oligomers, having a viscosity range of 1.5 cSt to 12 cSt. PAO fluids of particular use may include 3 cSt, 3.4 cSt, and/or 3.6 cSt and combinations thereof. Mixtures of PAO fluids having a viscosity range of 1.5 cSt to approximately 150 cSt or more may be used if desired. Unless indicated otherwise, all viscosities cited herein are measured at 100° C.

The PAO fluids may be conveniently made by the polymerization of an alphaolefin in the presence of a polymerization catalyst such as the Friedel-Crafts catalysts including, for example, aluminum trichloride, boron trifluoride or complexes of boron trifluoride with water, alcohols such as ethanol, propanol or butanol, carboxylic acids or esters such as ethyl acetate or ethyl propionate. For example the methods disclosed by U.S. Pat. No. 4,149,178 or 3,382,291 may be conveniently used herein. Other descriptions of PAO synthesis are found in the following U.S. Pat. Nos. 3,742,082; 3,769,363; 3,876,720; 4,239,930; 4,367,352; 4,413,156; 4,434,408; 4,910,355; 4,956,122; and 5,068,487. The dimers of the C₁₄ to C₁₈ olefins are described in U.S. Pat. No. 4,218,330.

Other useful lubricant oil base stocks include wax isomerate base stocks and base oils, comprising hydroisomerized waxy stocks (e.g. waxy stocks such as gas oils, slack waxes, fuels hydrocracker bottoms, etc.), hydroisomerized Fischer-Tropsch waxes, Gas-to-Liquids (GTL) base stocks and base oils, and other wax isomerate hydroisomerized base stocks and base oils, or mixtures thereof. Fischer-Tropsch waxes, the high boiling point residues of Fischer-Tropsch synthesis, are highly paraffinic hydrocarbons with very low sulfur content. The hydroprocessing used for the production of such base stocks may use an amorphous hydrocracking/hydroisomerization catalyst, such as one of the specialized lube hydrocracking (LHDC) catalysts or a crystalline hydrocracking/hydroisomerization catalyst, preferably a zeolitic catalyst. For example, one useful catalyst is ZSM-48 as described in U.S. Pat. No. 5,075,269, the disclosure of which is incorporated herein by reference in its entirety. Processes for making hydrocracked/hydroisomerized distillates and hydrocracked/hydroisomerized waxes are described, for example, in U.S. Pat. Nos. 2,817,693; 4,975,177; 4,921,594 and 4,897,178 as well as in British Patent Nos. 1,429,494; 1,350,257; 1,440,230 and 1,390,359. Each of the aforementioned patents is incorporated herein in their entirety. Particularly favorable processes are described in European Patent Application Nos. 464546 and 464547, also incorporated herein by reference. Processes using Fischer-Tropsch wax feeds are described in U.S. Pat. Nos. 4,594,172 and 4,943,672, the disclosures of which are incorporated herein by reference in their entirety.

Gas-to-Liquids (GTL) base oils, Fischer-Tropsch wax derived base oils, and other wax-derived hydroisomerized (wax isomerate) base oils be advantageously used in the instant disclosure, and may have useful kinematic viscosities at 100° C. of about 2 cSt to about 50 cSt, preferably about 2 cSt to about 30 cSt, more preferably about 3 cSt to about 25 cSt, as exemplified by GTL 4 with kinematic viscosity of about 4.0 cSt at 100° C. and a viscosity index of about 141. These Gas-to-Liquids (GTL) base oils, Fischer-Tropsch wax derived base oils, and other wax-derived hydroisomerized base oils may have useful pour points of about −20° C. or lower, and under some conditions may have advantageous pour points of about −25° C. or lower, with useful pour points of about −30° C. to about −40° C. or lower. Useful compositions of Gas-to-Liquids (GTL) base oils, Fischer-Tropsch wax derived base oils, and wax-derived hydroisomerized base oils are recited in U.S. Pat. Nos. 6,080,301; 6,090,989, and 6,165,949 for example, and are incorporated herein in their entirety by reference.

The hydrocarbyl aromatics can be used as a base oil or base oil component and can be any hydrocarbyl molecule that contains at least about 5% of its weight derived from an aromatic moiety such as a benzenoid moiety or naphthenoid moiety, or their derivatives. These hydrocarbyl aromatics include alkyl benzenes, alkyl naphthalenes, alkyl biphenyls, alkyl diphenyl oxides, alkyl naphthols, alkyl diphenyl sulfides, alkylated bis-phenol A, alkylated thiodiphenol, and the like. The aromatic can be mono-alkylated, dialkylated, polyalkylated, and the like. The aromatic can be mono- or poly-functionalized. The hydrocarbyl groups can also be comprised of mixtures of alkyl groups, alkenyl groups, alkynyl, cycloalkyl groups, cycloalkenyl groups and other related hydrocarbyl groups. The hydrocarbyl groups can range from about C₆ up to about C₆₀ with a range of about C₈ to about C₂₀ often being preferred. A mixture of hydrocarbyl groups is often preferred, and up to about three such substituents may be present. The hydrocarbyl group can optionally contain sulfur, oxygen, and/or nitrogen containing substituents. The aromatic group can also be derived from natural (petroleum) sources, provided at least about 5% of the molecule is comprised of an above-type aromatic moiety. Viscosities at 100° C. of approximately 2 cSt to about 50 cSt are preferred, with viscosities of approximately 3 cSt to about 20 cSt often being more preferred for the hydrocarbyl aromatic component. In one embodiment, an alkyl naphthalene where the alkyl group is primarily comprised of 1-hexadecene is used. Other alkylates of aromatics can be advantageously used. Naphthalene or methyl naphthalene, for example, can be alkylated with olefins such as octene, decene, dodecene, tetradecene or higher, mixtures of similar olefins, and the like. Alkylated naphthalene and analogues may also comprise compositions with isomeric distribution of alkylating groups on the alpha and beta carbon positions of the ring structure. Distribution of groups on the alpha and beta positions of a naphthalene ring may range from 100:1 to 1:100, more often 50:1 to 1:50 Useful concentrations of hydrocarbyl aromatic in a lubricant oil composition can be about 2% to about 25%, preferably about 4% to about 20%, and more preferably about 4% to about 15%, depending on the application.

Alkylated aromatics such as the hydrocarbyl aromatics of the present disclosure may be produced by well-known Friedel-Crafts alkylation of aromatic compounds. See Friedel-Crafts and Related Reactions, Olah, G. A. (ed.), Inter-science Publishers, New York, 1963. For example, an aromatic compound, such as benzene or naphthalene, is alkylated by an olefin, alkyl halide or alcohol in the presence of a Friedel-Crafts catalyst. See Friedel-Crafts and Related Reactions, Vol. 2, part 1, chapters 14, 17, and 18, See Olah, G. A. (ed.), Inter-science Publishers, New York, 1964. Many homogeneous or heterogeneous, solid catalysts are known to one skilled in the art. The choice of catalyst depends on the reactivity of the starting materials and product quality requirements. For example, strong acids such as AlCl₃, BF₃, or HF may be used. In some cases, milder catalysts such as FeCl₃ or SnCl₄ are preferred. Newer alkylation technology uses zeolites or solid super acids.

Esters comprise a useful base stock. Additive solvency and seal compatibility characteristics may be secured by the use of esters such as the esters of dibasic acids with monoalkanols and the polyol esters of monocarboxylic acids. Esters of the former type include, for example, the esters of dicarboxylic acids such as phthalic acid, succinic acid, alkyl succinic acid, alkenyl succinic acid, maleic acid, azelaic acid, suberic acid, sebacic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic acid, alkyl malonic acid, alkenyl malonic acid, etc., with a variety of alcohols such as butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, etc. Specific examples of these types of esters include dibutyl adipate, di(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, etc.

Particularly useful synthetic esters are those which are obtained by reacting one or more polyhydric alcohols, preferably the hindered polyols (such as the neopentyl polyols, e.g., neopentyl glycol, trimethylol ethane, 2-methyl-2-propyl-1,3-propanediol, trimethylol propane, pentaerythritol and dipentaerythritol) with alkanoic acids containing at least about 4 carbon atoms, preferably C₈ to C₃₀ acids such as saturated straight chain fatty acids including caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachic acid, and behenic acid, or the corresponding branched chain fatty acids or unsaturated fatty acids such as oleic acid, or mixtures of any of these materials.

Suitable synthetic ester components include the esters of trimethylol propane, trimethylol butane, trimethylol ethane, pentaerythritol and/or dipentaerythritol with one or more monocarboxylic acids containing from about 5 to about 10 carbon atoms. These esters are widely available commercially, for example, the Mobil P-41 and P-51 esters of ExxonMobil Chemical Company.

Also useful are esters derived from renewable material such as coconut, palm, rapeseed, soy, sunflower and the like. These esters may be monoesters, di-esters, polyol esters, complex esters, or mixtures thereof. These esters are widely available commercially, for example, the Mobil P-51 ester of ExxonMobil Chemical Company.

Engine oil formulations containing renewable esters are included in this disclosure. For such formulations, the renewable content of the ester is typically greater than about 70 weight percent, preferably more than about 80 weight percent and most preferably more than about 90 weight percent.

Other useful fluids of lubricating viscosity include non-conventional or unconventional base stocks that have been processed, preferably catalytically, or synthesized to provide high performance lubrication characteristics.

Non-conventional or unconventional base stocks/base oils include one or more of a mixture of base stock(s) derived from one or more Gas-to-Liquids (GTL) materials, as well as isomerate/isodewaxate base stock(s) derived from natural wax or waxy feeds, mineral and or non-mineral oil waxy feed stocks such as slack waxes, natural waxes, and waxy stocks such as gas oils, waxy fuels hydrocracker bottoms, waxy raffinate, hydrocrackate, thermal crackates, or other mineral, mineral oil, or even non-petroleum oil derived waxy materials such as waxy materials received from coal liquefaction or shale oil, and mixtures of such base stocks.

GTL materials are materials that are derived via one or more synthesis, combination, transformation, rearrangement, and/or degradation/deconstructive processes from gaseous carbon-containing compounds, hydrogen-containing compounds and/or elements as feed stocks such as hydrogen, carbon dioxide, carbon monoxide, water, methane, ethane, ethylene, acetylene, propane, propylene, propyne, butane, butylenes, and butynes. GTL base stocks and/or base oils are GTL materials of lubricating viscosity that are generally derived from hydrocarbons; for example, waxy synthesized hydrocarbons, that are themselves derived from simpler gaseous carbon-containing compounds, hydrogen-containing compounds and/or elements as feed stocks. GTL base stock(s) and/or base oil(s) include oils boiling in the lube oil boiling range (1) separated/fractionated from synthesized GTL materials such as, for example, by distillation and subsequently subjected to a final wax processing step which involves either or both of a catalytic dewaxing process, or a solvent dewaxing process, to produce lube oils of reduced/low pour point; (2) synthesized wax isomerates, comprising, for example, hydrodewaxed or hydroisomerized cat and/or solvent dewaxed synthesized wax or waxy hydrocarbons; (3) hydrodewaxed or hydroisomerized cat and/or solvent dewaxed Fischer-Tropsch (F-T) material (i.e., hydrocarbons, waxy hydrocarbons, waxes and possible analogous oxygenates); preferably hydrodewaxed or hydroisomerized/followed by cat and/or solvent dewaxing dewaxed F-T waxy hydrocarbons, or hydrodewaxed or hydroisomerized/followed by cat (or solvent) dewaxing dewaxed, F-T waxes, or mixtures thereof.

GTL base stock(s) and/or base oil(s) derived from GTL materials, especially, hydrodewaxed or hydroisomerized/followed by cat and/or solvent dewaxed wax or waxy feed, preferably F-T material derived base stock(s) and/or base oil(s), are characterized typically as having kinematic viscosities at 100° C. of from about 2 mm²/s to about 50 mm²/s (ASTM D445). They are further characterized typically as having pour points of −5° C. to about −40° C. or lower (ASTM D97). They are also characterized typically as having viscosity indices of about 80 to about 140 or greater (ASTM D2270).

In addition, the GTL base stock(s) and/or base oil(s) are typically highly paraffinic (>90% saturates), and may contain mixtures of monocycloparaffins and multicycloparaffins in combination with non-cyclic isoparaffins. The ratio of the naphthenic (i.e., cycloparaffin) content in such combinations varies with the catalyst and temperature used. Further, GTL base stock(s) and/or base oil(s) typically have very low sulfur and nitrogen content, generally containing less than about 10 ppm, and more typically less than about 5 ppm of each of these elements. The sulfur and nitrogen content of GTL base stock(s) and/or base oil(s) obtained from F-T material, especially F-T wax, is essentially nil. In addition, the absence of phosphorus and aromatics make this materially especially suitable for the formulation of low SAP products.

The term GTL base stock and/or base oil and/or wax isomerate base stock and/or base oil is to be understood as embracing individual fractions of such materials of wide viscosity range as recovered in the production process, mixtures of two or more of such fractions, as well as mixtures of one or two or more low viscosity fractions with one, two or more higher viscosity fractions to produce a blend wherein the blend exhibits a target kinematic viscosity.

The GTL material, from which the GTL base stock(s) and/or base oil(s) is/are derived is preferably an F-T material (i.e., hydrocarbons, waxy hydrocarbons, wax).

Optional base oils for use in the formulated lubricating oils useful in the present disclosure are any of the variety of oils corresponding to API Group I, Group II, Group III, Group IV, and Group V oils and mixtures thereof, preferably API Group II, Group III, Group IV, and Group V oils and mixtures thereof, more preferably the Group III to Group V base oils due to their exceptional volatility, stability, viscometric and cleanliness features. Minor quantities of Group I stock, such as the amount used to dilute additives for blending into formulated lube oil products, can be tolerated but should be kept to a minimum, i.e. amounts only associated with their use as diluent/carrier oil for additives used on an “as-received” basis. Even in regard to the Group II stocks, it is preferred that the Group II stock be in the higher quality range associated with that stock, i.e. a Group II stock having a viscosity index in the range 100<VI<120.

The optional base oil is typically is present in an amount ranging from about 6 to about 49 weight percent or from about 6 to about 45 weight percent, preferably from about 10 to about 49 weight percent or from about 20 to about 45 weight percent, and more preferably from about 25 to about 45 weight percent, based on the total weight of the composition. The optional base oil may be selected from any of the synthetic or natural oils typically used as crankcase lubricating oils for spark-ignited and compression-ignited engines. The optional base oil conveniently has a kinematic viscosity, according to ASTM standards, of about 2.5 cSt to about 18 cSt (or mm²/s) at 100° C. and preferably of about 2.5 cSt to about 12.5 cSt (or mm²/s) at 100° C., often more preferably from about 2.5 cSt to about 10 cSt. Mixtures of synthetic and natural base oils may be used if desired. Bi-modal, tri-modal, and additional combinations of mixtures of Group I, II, III, IV, and/or V base stocks may be used if desired.

Additives

The formulated lubricating oil useful in the present disclosure may additionally contain one or more of the other commonly used lubricating oil performance additives including but not limited to antiwear additives, dispersants, detergents, viscosity modifiers, corrosion inhibitors, rust inhibitors, metal deactivators, extreme pressure additives, anti-seizure agents, wax modifiers, viscosity modifiers, fluid-loss additives, seal compatibility agents, lubricity agents, anti-staining agents, chromophoric agents, defoamants, demulsifiers, densifiers, wetting agents, gelling agents, tackiness agents, colorants, and others. For a review of many commonly used additives, see Klamann in Lubricants and Related Products, Verlag Chemie, Deerfield Beach, Fla.; ISBN 0-89573-177-0. Reference is also made to “Lubricant Additives” by M. W. Ranney, published by Noyes Data Corporation of Parkridge, N J (1973); see also U.S. Pat. No. 7,704,930, the disclosure of which is incorporated herein in its entirety. These additives are commonly delivered with varying amounts of diluent oil, that may range from 5 weight percent to 50 weight percent.

The additives useful in this disclosure do not have to be soluble in the lubricating oils. Insoluble additives in oil can be dispersed in the lubricating oils of this disclosure.

The types and quantities of performance additives used in combination with the instant disclosure in lubricant compositions are not limited by the examples shown herein as illustrations.

Dispersants

During engine operation, oil-insoluble oxidation byproducts are produced. Dispersants help keep these byproducts in solution, thus diminishing their deposition on metal surfaces. Dispersants used in the formulation of the lubricating oil may be ashless or ash-forming in nature. Preferably, the dispersant is ashless. So called ashless dispersants are organic materials that form substantially no ash upon combustion. For example, non-metal-containing or borated metal-free dispersants are considered ashless. In contrast, metal-containing detergents discussed above form ash upon combustion.

Suitable dispersants typically contain a polar group attached to a relatively high molecular weight hydrocarbon chain. The polar group typically contains at least one element of nitrogen, oxygen, or phosphorus. Typical hydrocarbon chains contain 50 to 400 carbon atoms.

A particularly useful class of dispersants are the (poly)alkenylsuccinic derivatives, typically produced by the reaction of a long chain hydrocarbyl substituted succinic compound, usually a hydrocarbyl substituted succinic anhydride, with a polyhydroxy or polyamino compound. The long chain hydrocarbyl group constituting the oleophilic portion of the molecule which confers solubility in the oil, is normally a polyisobutylene group. Many examples of this type of dispersant are well known commercially and in the literature. Exemplary U.S. patents describing such dispersants are U.S. Pat. Nos. 3,172,892; 3,215,707; 3,219,666; 3,316,177; 3,341,542; 3,444,170; 3,454,607; 3,541,012; 3,630,904; 3,632,511; 3,787,374 and 4,234,435. Other types of dispersant are described in U.S. Pat. Nos. 3,036,003; 3,200,107; 3,254,025; 3,275,554; 3,438,757; 3,454,555; 3,565,804; 3,413,347; 3,697,574; 3,725,277; 3,725,480; 3,726,882; 4,454,059; 3,329,658; 3,449,250; 3,519,565; 3,666,730; 3,687,849; 3,702,300; 4,100,082; 5,705,458. A further description of dispersants may be found, for example, in European Patent Application No. 471 071, to which reference is made for this purpose.

Hydrocarbyl-substituted succinic acid and hydrocarbyl-substituted succinic anhydride derivatives are useful dispersants. In particular, succinimide, succinate esters, or succinate ester amides prepared by the reaction of a hydrocarbon-substituted succinic acid compound preferably having at least 50 carbon atoms in the hydrocarbon substituent, with at least one equivalent of an alkylene amine are particularly useful.

Succinimides are formed by the condensation reaction between hydrocarbyl substituted succinic anhydrides and amines. Molar ratios can vary depending on the polyamine. For example, the molar ratio of hydrocarbyl substituted succinic anhydride to TEPA can vary from about 1:1 to about 5:1. Representative examples are shown in U.S. Pat. Nos. 3,087,936; 3,172,892; 3,219,666; 3,272,746; 3,322,670; and 3,652,616, 3,948,800; and Canada Patent No. 1,094,044.

Succinate esters are formed by the condensation reaction between hydrocarbyl substituted succinic anhydrides and alcohols or polyols. Molar ratios can vary depending on the alcohol or polyol used. For example, the condensation product of a hydrocarbyl substituted succinic anhydride and pentaerythritol is a useful dispersant.

Succinate ester amides are formed by condensation reaction between hydrocarbyl substituted succinic anhydrides and alkanol amines. For example, suitable alkanol amines include ethoxylated polyalkylpolyamines, propoxylated polyalkylpolyamines and polyalkenylpolyamines such as polyethylene polyamines. One example is propoxylated hexamethylenediamine. Representative examples are shown in U.S. Pat. No. 4,426,305.

The molecular weight of the hydrocarbyl substituted succinic anhydrides used in the preceding paragraphs will typically range between 800 and 2,500 or more. The above products can be post-reacted with various reagents such as sulfur, oxygen, formaldehyde, carboxylic acids such as oleic acid. The above products can also be post reacted with boron compounds such as boric acid, borate esters or highly borated dispersants, to form borated dispersants generally having from about 0.1 to about 5 moles of boron per mole of dispersant reaction product.

Mannich base dispersants are made from the reaction of alkylphenols, formaldehyde, and amines. See U.S. Pat. No. 4,767,551, which is incorporated herein by reference. Process aids and catalysts, such as oleic acid and sulfonic acids, can also be part of the reaction mixture. Molecular weights of the alkylphenols range from 800 to 2,500. Representative examples are shown in U.S. Pat. Nos. 3,697,574; 3,703,536; 3,704,308; 3,751,365; 3,756,953; 3,798,165; and 3,803,039.

Typical high molecular weight aliphatic acid modified Mannich condensation products useful in this disclosure can be prepared from high molecular weight alkyl-substituted hydroxyaromatics or HNR₂ group-containing reactants.

Hydrocarbyl substituted amine ashless dispersant additives are well known to one skilled in the art; see, for example, U.S. Pat. Nos. 3,275,554; 3,438,757; 3,565,804; 3,755,433, 3,822,209, and 5,084,197.

Preferred dispersants include borated and non-borated succinimides, including those derivatives from mono-succinimides, bis-succinimides, and/or mixtures of mono- and bis-succinimides, wherein the hydrocarbyl succinimide is derived from a hydrocarbylene group such as polyisobutylene having a Mn of from about 500 to about 5000, or from about 1000 to about 3000, or about 1000 to about 2000, or a mixture of such hydrocarbylene groups, often with high terminal vinylic groups. Other preferred dispersants include succinic acid-esters and amides, alkylphenol-polyamine-coupled Mannich adducts, their capped derivatives, and other related components.

Polymethacrylate or polyacrylate derivatives are another class of dispersants. These dispersants are typically prepared by reacting a nitrogen containing monomer and a methacrylic or acrylic acid esters containing 5-25 carbon atoms in the ester group. Representative examples are shown in U.S. Pat. Nos. 2,100,993, and 6,323,164. Polymethacrylate and polyacrylate dispersants are normally used as multifunctional viscosity modifiers. The lower molecular weight versions can be used as lubricant dispersants or fuel detergents.

Illustrative preferred dispersants useful in this disclosure include those derived from polyalkenyl-substituted mono- or dicarboxylic acid, anhydride or ester, which dispersant has a polyalkenyl moiety with a number average molecular weight of at least 900 and from greater than 1.3 to 1.7, preferably from greater than 1.3 to 1.6, most preferably from greater than 1.3 to 1.5, functional groups (mono- or dicarboxylic acid producing moieties) per polyalkenyl moiety (a medium functionality dispersant). Functionality (F) can be determined according to the following formula:

F=(SAP×M_(n))/((112,200×A.I.)-(SAP×98))

wherein SAP is the saponification number (i.e., the number of milligrams of KOH consumed in the complete neutralization of the acid groups in one gram of the succinic-containing reaction product, as determined according to ASTM D94); M_(n) is the number average molecular weight of the starting olefin polymer; and A.I. is the percent active ingredient of the succinic-containing reaction product (the remainder being unreacted olefin polymer, succinic anhydride and diluent).

The polyalkenyl moiety of the dispersant may have a number average molecular weight of at least 900, suitably at least 1500, preferably between 1800 and 3000, such as between 2000 and 2800, more preferably from about 2100 to 2500, and most preferably from about 2200 to about 2400. The molecular weight of a dispersant is generally expressed in terms of the molecular weight of the polyalkenyl moiety. This is because the precise molecular weight range of the dispersant depends on numerous parameters including the type of polymer used to derive the dispersant, the number of functional groups, and the type of nucleophilic group employed.

Polymer molecular weight, specifically M_(n), can be determined by various known techniques. One convenient method is gel permeation chromatography (GPC), which additionally provides molecular weight distribution information (see W. W. Yau, J. J. Kirkland and D. D. Bly, “Modern Size Exclusion Liquid Chromatography”, John Wiley and Sons, New York, 1979). Another useful method for determining molecular weight, particularly for lower molecular weight polymers, is vapor pressure osmometry (e.g., ASTM D3592).

The polyalkenyl moiety in a dispersant preferably has a narrow molecular weight distribution (MWD), also referred to as polydispersity, as determined by the ratio of weight average molecular weight (M_(w)) to number average molecular weight (M_(n)). Polymers having a M_(w)/M_(n) of less than 2.2, preferably less than 2.0, are most desirable. Suitable polymers have a polydispersity of from about 1.5 to 2.1, preferably from about 1.6 to about 1.8.

Suitable polyalkenes employed in the formation of the dispersants include homopolymers, interpolymers or lower molecular weight hydrocarbons. One family of such polymers comprise polymers of ethylene and/or at least one C₃ to C₂ alpha-olefin having the formula H₂C═CHR¹ wherein R¹ is a straight or branched chain alkyl radical comprising 1 to 26 carbon atoms and wherein the polymer contains carbon-to-carbon unsaturation, and a high degree of terminal ethenylidene unsaturation. Preferably, such polymers comprise interpolymers of ethylene and at least one alpha-olefin of the above formula, wherein R¹ is alkyl of from 1 to 18 carbon atoms, and more preferably is alkyl of from 1 to 8 carbon atoms, and more preferably still of from 1 to 2 carbon atoms.

Another useful class of polymers is polymers prepared by cationic polymerization of monomers such as isobutene and styrene. Common polymers from this class include polyisobutenes obtained by polymerization of a C₄ refinery stream having a butene content of 35 to 75% by wt., and an isobutene content of 30 to 60% by wt. A preferred source of monomer for making poly-n-butenes is petroleum feedstreams such as Raffinate II. These feedstocks are disclosed in the art such as in U.S. Pat. No. 4,952,739. A preferred embodiment utilizes polyisobutylene prepared from a pure isobutylene stream or a Raffinate I stream to prepare reactive isobutylene polymers with terminal vinylidene olefins. Polyisobutene polymers that may be employed are generally based on a polymer chain of from 1500 to 3000.

The dispersant(s) are preferably non-polymeric (e.g., mono- or bis-succinimides). Such dispersants can be prepared by conventional processes such as disclosed in U.S. Patent Application Publication No. 2008/0020950, the disclosure of which is incorporated herein by reference.

The dispersant(s) can be borated by conventional means, as generally disclosed in U.S. Pat. Nos. 3,087,936, 3,254,025 and 5,430,105.

Such dispersants may be used in an amount of about 0.01 to 20 weight percent or 0.01 to 10 weight percent, preferably about 0.5 to 8 weight percent, or more preferably 0.5 to 4 weight percent. Or such dispersants may be used in an amount of about 2 to 12 weight percent, preferably about 4 to 10 weight percent, or more preferably 6 to 9 weight percent. On an active ingredient basis, such additives may be used in an amount of about 0.06 to 14 weight percent, preferably about 0.3 to 6 weight percent. The hydrocarbon portion of the dispersant atoms can range from C₆₀ to C₁₀₀₀, or from C₇₀ to C₃₀₀, or from C₇₀ to C₂₀₀. These dispersants may contain both neutral and basic nitrogen, and mixtures of both. Dispersants can be end-capped by borates and/or cyclic carbonates. Nitrogen content in the finished oil can vary from about 200 ppm by weight to about 2000 ppm by weight, preferably from about 200 ppm by weight to about 1200 ppm by weight. Basic nitrogen can vary from about 100 ppm by weight to about 1000 ppm by weight, preferably from about 100 ppm by weight to about 600 ppm by weight.

Dispersants as described herein are beneficially useful with the compositions of this disclosure and substitute for some or all of the surfactants of this disclosure. Further, in one embodiment, preparation of the compositions of this disclosure using one or more dispersants is achieved by combining ingredients of this disclosure, plus optional base stocks and lubricant additives, in a mixture at a temperature above the melting point of such ingredients, particularly that of the one or more M-carboxylates (M=H, metal, two or more metals, mixtures thereof).

As used herein, the dispersant concentrations are given on an “as delivered” basis. Typically, the active dispersant is delivered with a process oil. The “as delivered” dispersant typically contains from about 20 weight percent to about 80 weight percent, or from about 40 weight percent to about 60 weight percent, of active dispersant in the “as delivered” dispersant product.

Detergents

Illustrative detergents useful in this disclosure include, for example, alkali metal detergents, alkaline earth metal detergents, or mixtures of one or more alkali metal detergents and one or more alkaline earth metal detergents. A typical detergent is an anionic material that contains a long chain hydrophobic portion of the molecule and a smaller anionic or oleophobic hydrophilic portion of the molecule. The anionic portion of the detergent is typically derived from an organic acid such as a sulfur-containing acid, carboxylic acid (e.g., salicylic acid), phosphorus-containing acid, phenol, or mixtures thereof. The counterion is typically an alkaline earth or alkali metal. The detergent can be overbased as described herein.

The detergent is preferably a metal salt of an organic or inorganic acid, a metal salt of a phenol, or mixtures thereof. The metal is preferably selected from an alkali metal, an alkaline earth metal, and mixtures thereof. The organic or inorganic acid is selected from an aliphatic organic or inorganic acid, a cycloaliphatic organic or inorganic acid, an aromatic organic or inorganic acid, and mixtures thereof.

The metal is preferably selected from an alkali metal, an alkaline earth metal, and mixtures thereof. More preferably, the metal is selected from calcium (Ca), magnesium (Mg), and mixtures thereof.

The organic acid or inorganic acid is preferably selected from a sulfur-containing acid, a carboxylic acid, a phosphorus-containing acid, and mixtures thereof.

Preferably, the metal salt of an organic or inorganic acid or the metal salt of a phenol comprises calcium phenate, calcium sulfonate, calcium salicylate, magnesium phenate, magnesium sulfonate, magnesium salicylate, an overbased detergent, and mixtures thereof.

Salts that contain a substantially stochiometric amount of the metal are described as neutral salts and have a total base number (TBN, as measured by ASTM D2896) of from 0 to 80. Many compositions are overbased, containing large amounts of a metal base that is achieved by reacting an excess of a metal compound (a metal hydroxide or oxide, for example) with an acidic gas (such as carbon dioxide). Useful detergents can be neutral, mildly overbased, or highly overbased. These detergents can be used in mixtures of neutral, overbased, highly overbased calcium salicylate, sulfonates, phenates and/or magnesium salicylate, sulfonates, phenates. The TBN ranges can vary from low, medium to high TBN products, including as low as 0 to as high as 600. Preferably the TBN delivered by the detergent is between 1 and 20. More preferably between 1 and 12. Mixtures of low, medium, high TBN can be used, along with mixtures of calcium and magnesium metal based detergents, and including sulfonates, phenates, salicylates, and carboxylates. A detergent mixture with a metal ratio of 1, in conjunction of a detergent with a metal ratio of 2, and as high as a detergent with a metal ratio of 5, can be used. Borated detergents can also be used.

Alkaline earth phenates are another useful class of detergent. These detergents can be made by reacting alkaline earth metal hydroxide or oxide (CaO, Ca(OH)₂, BaO, Ba(OH)₂, MgO, Mg(OH)₂, for example) with an alkyl phenol or sulfurized alkylphenol. Useful alkyl groups include straight chain or branched C₁-C₃₀ alkyl groups, preferably, C₄-C₂₀ or mixtures thereof Examples of suitable phenols include isobutylphenol, 2-ethylhexylphenol, nonylphenol, dodecyl phenol, and the like. It should be noted that starting alkylphenols may contain more than one alkyl substituent that are each independently straight chain or branched and can be used from 0.5 to 6 weight percent. When a non-sulfurized alkylphenol is used, the sulfurized product may be obtained by methods well known in the art. These methods include heating a mixture of alkylphenol and sulfurizing agent (including elemental sulfur, sulfur halides such as sulfur dichloride, and the like) and then reacting the sulfurized phenol with an alkaline earth metal base.

In accordance with this disclosure, metal salts of carboxylic acids are preferred detergents. These carboxylic acid detergents may be prepared by reacting a basic metal compound with at least one carboxylic acid and removing free water from the reaction product. These compounds may be overbased to produce the desired TBN level. Detergents made from salicylic acid are one preferred class of detergents derived from carboxylic acids. Useful salicylates include long chain alkyl salicylates. One useful family of compositions is of the formula

where R is an alkyl group having 1 to about 30 carbon atoms, n is an integer from 1 to 4, and M is an alkaline earth metal. Preferred R groups are alkyl chains of at least C₁₁, preferably C₁₃ or greater. R may be optionally substituted with substituents that do not interfere with the detergent's function. M is preferably, calcium, magnesium, barium, or mixtures thereof. More preferably, M is calcium.

Hydrocarbyl-substituted salicylic acids may be prepared from phenols by the Kolbe reaction (see U.S. Pat. No. 3,595,791). The metal salts of the hydrocarbyl-substituted salicylic acids may be prepared by double decomposition of a metal salt in a polar solvent such as water or alcohol.

Alkaline earth metal phosphates are also used as detergents and are known in the art.

Detergents may be simple detergents or what is known as hybrid or complex detergents. The latter detergents can provide the properties of two detergents without the need to blend separate materials. See U.S. Pat. No. 6,034,039.

Preferred detergents include calcium sulfonates, magnesium sulfonates, calcium salicylates, magnesium salicylates, calcium phenates, magnesium phenates, and other related components (including borated detergents), and mixtures thereof. Preferred mixtures of detergents include magnesium sulfonate and calcium salicylate, magnesium sulfonate and calcium sulfonate, magnesium sulfonate and calcium phenate, calcium phenate and calcium salicylate, calcium phenate and calcium sulfonate, calcium phenate and magnesium salicylate, calcium phenate and magnesium phenate. Overbased detergents are also preferred.

The detergent concentration in the lubricating oils of this disclosure can range from about 0.5 to about 6.0 weight percent, preferably about 0.6 to 5.0 weight percent, and more preferably from about 0.8 weight percent to about 4.0 weight percent, based on the total weight of the lubricating oil.

As used herein, the detergent concentrations are given on an “as delivered” basis. Typically, the active detergent is delivered with a process oil. The “as delivered” detergent typically contains from about 20 weight percent to about 100 weight percent, or from about 40 weight percent to about 60 weight percent, of active detergent in the “as delivered” detergent product.

Antiwear Additives

A metal alkylthiophosphate and more particularly a metal dialkyl dithio phosphate in which the metal constituent is zinc, or zinc dialkyl dithio phosphate (ZDDP) can be a useful component of the lubricating oils of this disclosure. ZDDP can be derived from primary alcohols, secondary alcohols or mixtures thereof. ZDDP compounds generally are of the formula

Zn[SP(S)(OR¹)(OR²)]₂

where R¹ and R² are C₁-C₁₈ alkyl groups, preferably C₂-C₁₂ alkyl groups. These alkyl groups may be straight chain or branched. Alcohols used in the ZDDP can be propanol, 2-propanol, butanol, secondary butanol, pentanols, hexanols such as 4-methyl-2-pentanol, n-hexanol, n-octanol, 2-ethyl hexanol, alkylated phenols, and the like. Mixtures of secondary alcohols or of primary and secondary alcohol can be preferred. Alkyl aryl groups may also be used.

Preferable zinc dithiophosphates which are commercially available include secondary zinc dithiophosphates such as those available from for example, The Lubrizol Corporation under the trade designations “LZ 677A”, “LZ 1095” and “LZ 1371”, from for example Chevron Oronite under the trade designation “OLOA 262” and from for example Afton Chemical under the trade designation “HITEC 7169”.

The ZDDP is typically used in amounts of from about 0.3 weight percent to about 1.5 weight percent, preferably from about 0.4 weight percent to about 1.2 weight percent, more preferably from about 0.5 weight percent to about 1.0 weight percent, and even more preferably from about 0.6 weight percent to about 0.8 weight percent, based on the total weight of the lubricating oil, although more or less can often be used advantageously. Preferably, the ZDDP is a secondary ZDDP and present in an amount of from about 0.6 to 1.0 weight percent of the total weight of the lubricating oil.

Viscosity Modifiers

Viscosity modifiers (also known as viscosity index improvers (VI improvers), and viscosity improvers) can be included in the lubricant compositions of this disclosure.

Viscosity modifiers provide lubricants with high and low temperature operability. These additives impart shear stability at elevated temperatures and acceptable viscosity at low temperatures.

Suitable viscosity modifiers include high molecular weight hydrocarbons, polyesters and viscosity modifier dispersants that function as both a viscosity modifier and a dispersant. Typical molecular weights of these polymers are between about 10,000 to 1,500,000, more typically about 20,000 to 1,200,000, and even more typically between about 50,000 and 1,000,000.

Examples of suitable viscosity modifiers are linear or star-shaped polymers and copolymers of methacrylate, butadiene, olefins, or alkylated styrenes. Polyisobutylene is a commonly used viscosity modifier. Another suitable viscosity modifier is polymethacrylate (copolymers of various chain length alkyl methacrylates, for example), some formulations of which also serve as pour point depressants. Other suitable viscosity modifiers include copolymers of ethylene and propylene, hydrogenated block copolymers of styrene and isoprene, and polyacrylates (copolymers of various chain length acrylates, for example). Specific examples include styrene-isoprene or styrene-butadiene based polymers of 50,000 to 200,000 molecular weight.

Olefin copolymers are commercially available from Chevron Oronite Company LLC under the trade designation “PARATONE®” (such as “PARATONE® 8921” and “PARATONE® 8941”); from Afton Chemical Corporation under the trade designation “HiTEC®” (such as “HiTEC® 5850B”; and from The Lubrizol Corporation under the trade designation “Lubrizol® 7067C”. Hydrogenated polyisoprene star polymers are commercially available from Infineum International Limited, e.g., under the trade designation “SV200” and “SV600”. Hydrogenated diene-styrene block copolymers are commercially available from Infineum International Limited, e.g., under the trade designation “SV 50”.

The polymethacrylate or polyacrylate polymers can be linear polymers which are available from Evnoik Industries under the trade designation “Viscoplex®” (e.g., Viscoplex 6-954) or star polymers which are available from Lubrizol Corporation under the trade designation Asteric™ (e.g., Lubrizol 87708 and Lubrizol 87725).

Illustrative vinyl aromatic-containing polymers useful in this disclosure may be derived predominantly from vinyl aromatic hydrocarbon monomer. Illustrative vinyl aromatic-containing copolymers useful in this disclosure may be represented by the following general formula:

A-B

wherein A is a polymeric block derived predominantly from vinyl aromatic hydrocarbon monomer, and B is a polymeric block derived predominantly from conjugated diene monomer.

In an embodiment of this disclosure, the viscosity modifiers may be used in an amount of less than about 10 weight percent, preferably less than about 7 weight percent, more preferably less than about 4 weight percent, and in certain instances, may be used at less than 2 weight percent, preferably less than about 1 weight percent, and more preferably less than about 0.5 weight percent, based on the total weight of the formulated oil or lubricating engine oil. Viscosity modifiers are typically added as concentrates, in large amounts of diluent oil.

As used herein, the viscosity modifier concentrations are given on an “as delivered” basis. Typically, the active polymer is delivered with a diluent oil. The “as delivered” viscosity modifier typically contains from 20 weight percent to 75 weight percent of an active polymer for polymethacrylate or polyacrylate polymers, or from 8 weight percent to 20 weight percent of an active polymer for olefin copolymers, hydrogenated polyisoprene star polymers, or hydrogenated diene-styrene block copolymers, in the “as delivered” polymer concentrate.

Antioxidants

Antioxidants retard the oxidative degradation of base oils during service. Such degradation may result in deposits on metal surfaces, the presence of sludge, or a viscosity increase in the lubricant. One skilled in the art knows a wide variety of oxidation inhibitors that are useful in lubricating oil compositions. See, Klamann in Lubricants and Related Products, op cite, and U.S. Pat. Nos. 4,798,684 and 5,084,197, for example.

Useful antioxidants include hindered phenols. These phenolic antioxidants may be ashless (metal-free) phenolic compounds or neutral or basic metal salts of certain phenolic compounds. Typical phenolic antioxidant compounds are the hindered phenolics which are the ones which contain a sterically hindered hydroxyl group, and these include those derivatives of dihydroxy aryl compounds in which the hydroxyl groups are in the o- or p-position to each other. Typical phenolic antioxidants include the hindered phenols substituted with C₆+ alkyl groups and the alkylene coupled derivatives of these hindered phenols. Examples of phenolic materials of this type 2-t-butyl-4-heptyl phenol; 2-t-butyl-4-octyl phenol; 2-t-butyl-4-dodecyl phenol; 2,6-di-t-butyl-4-heptyl phenol; 2,6-di-t-butyl-4-dodecyl phenol; 2-methyl-6-t-butyl-4-heptyl phenol; and 2-methyl-6-t-butyl-4-dodecyl phenol. Other useful hindered mono-phenolic antioxidants may include for example hindered 2,6-di-alkyl-phenolic proprionic ester derivatives. Bis-phenolic antioxidants may also be advantageously used in combination with the instant disclosure. Examples of ortho-coupled phenols include: 2,2′-bis(4-heptyl-6-t-butyl-phenol); 2,2′-bis(4-octyl-6-t-butyl-phenol); and 2,2′-bis(4-dodecyl-6-t-butyl-phenol). Para-coupled bisphenols include for example 4,4′-bis(2,6-di-t-butyl phenol) and 4,4′-methylene-bis(2,6-di-t-butyl phenol).

Effective amounts of one or more catalytic antioxidants may also be used. The catalytic antioxidants comprise an effective amount of a) one or more oil soluble polymetal organic compounds; and, effective amounts of b) one or more substituted N,N′-diaryl-o-phenylenediamine compounds or c) one or more hindered phenol compounds; or a combination of both b) and c). Catalytic antioxidants are more fully described in U.S. Pat. No. 8,048,833, herein incorporated by reference in its entirety.

Non-phenolic oxidation inhibitors which may be used include aromatic amine antioxidants and these may be used either as such or in combination with phenolics. Typical examples of non-phenolic antioxidants include: alkylated and non-alkylated aromatic amines such as aromatic monoamines of the formula R⁸R⁹R¹⁰N where R⁸ is an aliphatic, aromatic or substituted aromatic group, R⁹ is an aromatic or a substituted aromatic group, and R¹⁰ is H, alkyl, aryl or R¹¹S(O)xR¹² where R₁₁ is an alkylene, alkenylene, or aralkylene group, R¹² is a higher alkyl group, or an alkenyl, aryl, or alkaryl group, and x is 0, 1 or 2. The aliphatic group R⁸ may contain from 1 to about 20 carbon atoms, and preferably contains from about 6 to 12 carbon atoms. The aliphatic group is a saturated aliphatic group. Preferably, both R⁸ and R⁹ are aromatic or substituted aromatic groups, and the aromatic group may be a fused ring aromatic group such as naphthyl. Aromatic groups R⁸ and R⁹ may be joined together with other groups such as S.

Typical aromatic amines antioxidants have alkyl substituent groups of at least about 6 carbon atoms. Examples of aliphatic groups include hexyl, heptyl, octyl, nonyl, and decyl. Generally, the aliphatic groups will not contain more than about 14 carbon atoms. The general types of amine antioxidants useful in the present compositions include diphenylamines, phenyl naphthylamines, phenothiazines, imidodibenzyls and diphenyl phenylene diamines. Mixtures of two or more aromatic amines are also useful. Polymeric amine antioxidants can also be used. Particular examples of aromatic amine antioxidants useful in the present disclosure include: p,p′-dioctyldiphenylamine; t-octylphenyl-alpha-naphthylamine; phenyl-alphanaphthylamine; and p-octylphenyl-alpha-naphthylamine.

Sulfurized alkyl phenols and alkali or alkaline earth metal salts thereof also are useful antioxidants.

Preferred antioxidants include hindered phenols, arylamines. These antioxidants may be used individually by type or in combination with one another. Such additives may be used in an amount of about 0.01 to 5 weight percent, preferably about 0.01 to 1.5 weight percent, more preferably zero to less than 1.5 weight percent, more preferably zero to less than 1 weight percent.

Pour Point Depressants (PPDs)

Conventional pour point depressants (also known as lube oil flow improvers) may be added to the compositions of the present disclosure if desired. These pour point depressant may be added to lubricating compositions of the present disclosure to lower the minimum temperature at which the fluid will flow or can be poured. Examples of suitable pour point depressants include polymethacrylates, polyacrylates, polyarylamides, condensation products of haloparaffin waxes and aromatic compounds, vinyl carboxylate polymers, and terpolymers of dialkylfumarates, vinyl esters of fatty acids and allyl vinyl ethers. U.S. Pat. Nos. 1,815,022; 2,015,748; 2,191,498; 2,387,501; 2,655, 479; 2,666,746; 2,721,877; 2,721,878; and 3,250,715 describe useful pour point depressants and/or the preparation thereof. Such additives may be used in an amount of about 0.01 to 5 weight percent, preferably about 0.01 to 1.5 weight percent.

Seal Compatibility Agents

Seal compatibility agents help to swell elastomeric seals by causing a chemical reaction in the fluid or physical change in the elastomer. Suitable seal compatibility agents for lubricating oils include organic phosphates, aromatic esters, aromatic hydrocarbons, esters (butylbenzyl phthalate, for example), and polybutenyl succinic anhydride. Such additives may be used in an amount of about 0.01 to 3 weight percent, preferably about 0.01 to 2 weight percent.

Antifoam Agents

Anti-foam agents may advantageously be added to lubricant compositions. These agents retard the formation of stable foams. Silicones and organic polymers are typical anti-foam agents. For example, polysiloxanes, such as silicon oil or polydimethyl siloxane, provide antifoam properties. Anti-foam agents are commercially available and may be used in conventional minor amounts along with other additives such as demulsifiers; usually the amount of these additives combined is less than 1 weight percent and often less than 0.1 weight percent.

Inhibitors and Antirust Additives

Antirust additives (or corrosion inhibitors) are additives that protect lubricated metal surfaces against chemical attack by water or other contaminants. A wide variety of these are commercially available.

One type of antirust additive is a polar compound that wets the metal surface preferentially, protecting it with a film of oil. Another type of antirust additive absorbs water by incorporating it in a water-in-oil emulsion so that only the oil touches the metal surface. Yet another type of antirust additive chemically adheres to the metal to produce a non-reactive surface. Examples of suitable additives include zinc dithiophosphates, metal phenolates, basic metal sulfonates, fatty acids and amines. Such additives may be used in an amount of about 0.01 to 5 weight percent, preferably about 0.01 to 1.5 weight percent.

Friction Modifiers

A friction modifier is any material or materials that can alter the coefficient of friction of a surface lubricated by any lubricant or fluid containing such material(s). Friction modifiers, also known as friction reducers, or lubricity agents or oiliness agents, and other such agents that change the ability of base oils, formulated lubricant compositions, or functional fluids, to modify the coefficient of friction of a lubricated surface may be effectively used in combination with the base oils or lubricant compositions of the present disclosure if desired. Friction modifiers that lower the coefficient of friction are particularly advantageous in combination with the base oils and lube compositions of this disclosure.

Illustrative friction modifiers may include, for example, organometallic compounds or materials, or mixtures thereof. Illustrative organometallic friction modifiers useful in the lubricating engine oil formulations of this disclosure include, for example, molybdenum amine, molybdenum diamine, an organotungstenate, a molybdenum dithiocarbamate, molybdenum dithiophosphates, molybdenum amine complexes, molybdenum carboxylates, and the like, and mixtures thereof. Similar tungsten based compounds may be preferable.

Other illustrative friction modifiers useful in the lubricating engine oil formulations of this disclosure include, for example, alkoxylated fatty acid esters, alkanolamides, polyol fatty acid esters, borated glycerol fatty acid esters, fatty alcohol ethers, and mixtures thereof.

Illustrative alkoxylated fatty acid esters include, for example, polyoxyethylene stearate, fatty acid polyglycol ester, and the like. These can include polyoxypropylene stearate, polyoxybutylene stearate, polyoxyethylene isosterate, polyoxypropylene isostearate, polyoxyethylene palmitate, and the like.

Illustrative alkanolamides include, for example, lauric acid diethylalkanolamide, palmic acid diethylalkanolamide, and the like. These can include oleic acid diethyalkanolamide, stearic acid diethylalkanolamide, oleic acid diethylalkanolamide, polyethoxylated hydrocarbylamides, polypropoxylated hydrocarbylamides, and the like.

Illustrative polyol fatty acid esters include, for example, glycerol mono-oleate, saturated mono-, di-, and tri-glyceride esters, glycerol mono-stearate, and the like. These can include polyol esters, hydroxyl-containing polyol esters, and the like. Illustrative borated glycerol fatty acid esters include, for example, borated glycerol mono-oleate, borated saturated mono-, di-, and tri-glyceride esters, borated glycerol mono-sterate, and the like. In addition to glycerol polyols, these can include trimethylolpropane, pentaerythritol, sorbitan, and the like. These esters can be polyol monocarboxylate esters, polyol dicarboxylate esters, and on occasion polyoltricarboxylate esters. Preferred can be the glycerol mono-oleates, glycerol dioleates, glycerol trioleates, glycerol monostearates, glycerol distearates, and glycerol tristearates and the corresponding glycerol monopalmitates, glycerol dipalmitates, and glycerol tripalmitates, and the respective isostearates, linoleates, and the like. On occasion the glycerol esters can be preferred as well as mixtures containing any of these. Ethoxylated, propoxylated, butoxylated fatty acid esters of polyols, especially using glycerol as underlying polyol can be preferred.

Illustrative fatty alcohol ethers include, for example, stearyl ether, myristyl ether, and the like. Alcohols, including those that have carbon numbers from C₃ to C₅₀, can be ethoxylated, propoxylated, or butoxylated to form the corresponding fatty alkyl ethers. The underlying alcohol portion can preferably be stearyl, myristyl, C₁₁-C₁₃ hydrocarbon, oleyl, isosteryl, and the like.

The lubricating oils of this disclosure exhibit desired properties, e.g., wear control, in the presence or absence of a friction modifier.

Useful concentrations of friction modifiers may range from 0.01 weight percent to 5 weight percent, or about 0.1 weight percent to about 2.5 weight percent, or about 0.1 weight percent to about 1.5 weight percent, or about 0.1 weight percent to about 1 weight percent. Concentrations of molybdenum-containing materials are often described in terms of Mo metal concentration. Advantageous concentrations of Mo may range from 25 ppm to 700 ppm or more, and often with a preferred range of 50-200 ppm. Friction modifiers of all types may be used alone or in mixtures with the materials of this disclosure. Often mixtures of two or more friction modifiers, or mixtures of friction modifier(s) with alternate surface active material(s), are also desirable.

When lubricating oil compositions contain one or more of the additives discussed above, the additive(s) are blended into the composition in an amount sufficient for it to perform its intended function. Typical amounts of such additives useful in the present disclosure are shown in Table 1 below.

It is noted that many of the additives are shipped from the additive manufacturer as a concentrate, containing one or more additives together, with a certain amount of base oil diluents. Accordingly, the weight amounts in the table below, as well as other amounts mentioned herein, are directed to the amount of active ingredient (that is the non-diluent portion of the ingredient). The weight percent (wt. %) indicated below is based on the total weight of the lubricating oil composition.

TABLE 1 Typical Amounts of Other Lubricating Oil Components Approximate Approximate Compound Wt. % (Useful) Wt. % (Preferred) Dispersant  0.1-20 0.1-8  Detergent  0.1-20 0.1-8  Friction Modifier 0.01-5  0.01-1.5 Antioxidant 0.1-5  0.1-1.5 Pour Point Depressant (PPD) 0.0-5 0.01-1.5 Anti-foam Agent 0.001-3  0.001-0.15 Viscosity Modifier (solid 0.1-2 0.1-1  polymer basis) Antiwear 0.2-3 0.5-1  Inhibitor and Antirust 0.01-5  0.01-1.5

The foregoing additives are all commercially available materials. These additives may be added independently but are usually precombined in packages which can be obtained from suppliers of lubricant oil additives. Additive packages with a variety of ingredients, proportions and characteristics are available and selection of the appropriate package will take the requisite use of the ultimate composition into account.

The following non-limiting examples are provided to illustrate the disclosure.

Examples

Formulations were prepared as described herein. All of the ingredients used herein are commercially available.

The lubricating oil base stocks used in the formulations were liquid crystal base oils defined in FIGS. 1 and 2, PAO base oils, and PAG base oils.

The additive package used in the formulations included conventional additives in conventional amounts. Conventional additives used in the formulations were one or more of an antioxidant, dispersant, detergent, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, anti-foam agent, inhibitor, anti-rust additive, optional friction modifier, optional antiwear additive, and other optional lubricant performances additives.

Base oils were identified which produce films under sliding/rolling contacts in a ball-on-disk test on a mini-traction machine (MTM). Friction coefficient and film thickness were measured in the tests. The test conditions are summarized in Table 2 below.

TABLE 2 Test Type Ball-on-Disk, Mini Traction Machine Test Description Constant Rolling Speed, Various SRR Ball/Disk Motion Co-Motion Ball Material/Roughness/Radius AISI 52100/<0.02 μm/19.05 mm Disk Material/Roughness/Radius AISI 52100/<0.01 μm/46 mm Temperature 40° C. to 140° C. Pressure 0.75 GPa to 1.25 GPa Rolling Speed 2 m/s Slide to Roll Ratio (SRR) 0% to 100%

The use of a low traction base stock comprised of liquid crystals such as S2 or analogs with differing R group side chains or differing core structure still containing two rings (see FIG. 1), at least one aromatic, with or without additional additives or base stocks present to give lower traction compared to non-liquid crystal hydrocarbon fluids of the same viscosities. Clear gains (lower friction coefficients) are shown in FIG. 3 using the S-series type liquid crystals. In the nearly pure rolling condition (0% SRR), liquid crystals appear to have slightly higher traction, but with any sliding they have very low traction compared to other fluids. Overall average traction is compared to PAO4 and is shown in FIG. 4.

FIG. 3 graphically depicts friction coefficient over 0-100% slide-to-roll ratio (SRR), a temperature of 100° C., and a pressure of 1 GPa, on MTM traction test for a low viscosity PAG (4 cSt at 100° C., squares), two PAO fluids (8 cSt, circles, and 4 cSt, triangles) and four liquid crystal materials: D1 (diamonds), S2 (short dash line), S8 (continuous line), S11 (long dash line).

As a base stock, the S-series fluids clearly show performance gains over 4 cSt PAO and 4 cSt oil soluble PAG (FIG. 3).

FIG. 4 shows average traction coefficient for low viscosity PAG, two PAO fluids, and four liquid crystal materials, over 0-100% slide-to-roll ratio (SRR) compared to PAO4.

FIG. 5 graphically depicts friction coefficient versus pressure at slide-to-roll ratio (SRR) 30% and constant temperature of 80° C. in MTM traction test for liquid crystals S2 and 8CB as well as PAO 3.6.

FIG. 6 graphically depicts friction coefficient versus temperature at slide-to-roll ratio (SRR) 30% and constant 1.0 GPa Hertzian pressure for liquid crystals S2 and 8CB and conventional fluid PAO 3.6.

FIG. 7 graphically depicts elastohydrodynamic lubrication (EHL) film thickness versus rolling speed (mm/s) for S2 and PAO4 at two temperatures (i.e., 40° C. and 100° C.). PAO4 has KV40 of 18.5 cSt and KV100 of 4.1 cSt. S2 has KV40 of 15.2 cSt and KV100 of 3.9 cSt. Although KV100 of S2 is lower at 100° C., EHL film appears to be of greater thickness.

EHL film thickness results (FIG. 7) show that in the pure rolling EHL condition, thicker films may be forming than would be expected for the fluid viscosity. FIGS. 5 and 6 demonstrate pressure and temperature effects on traction differentiation of S series fluids. S series shows clear gains at all conditions tested, and higher pressures and lower temperatures appear most favorable.

It was surprisingly found that the liquid crystal benefits extend to blends. A 67% blend of S2 with a high viscosity copolymer (KV40 445 cSt; KV100 60 cSt) shows improvement over a blend with PAO4 at same treat rate even though the latter has lower viscosity (KV40 409 cSt; KV100 52 cSt). The PAO2 blend has similar viscosity to the S2 blend (KV40 432 cSt; KV100 64 cSt). However, the S2 blend still maintains superior performance. (see FIGS. 8-12).

Furthermore, the liquid crystal S2 could be used to improve the traction performance of low viscosity basestock, such as 4 cSt PAO as illustrated by MTM testing traction performance of gradual mixtures of theses 2 components. (see FIGS. 13 and 14)

FIG. 8 shows bimodal blends prepared from a high viscosity copolymer, PAO2, PAO4, S2, and an additive package.

FIG. 9 graphically depicts friction coefficient over 0-100% slide-to-roll ratio (SRR) in MTM traction for bimodal blends of similar viscosity (˜460 cSt at 40° C.). The bimodal blends include PAO2 (squares), PAO4 (triangles) S2 (circles) and a commercial gear and bearing oil (diamonds). In friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 40° C., and a pressure of 0.75 GPa, the friction coefficient is less than about 0.02. PAO4 and S2 were used at 67% treat in the blends. S2 outperforms the PAO4 blend despite slightly higher kinematic viscosity.

FIG. 10 graphically depicts friction coefficient over 0-100% slide-to-roll ratio (SRR) in MTM traction for bimodal blends of similar viscosity (˜460 cSt at 40° C.). The bimodal blends include PAO2 (squares), PAO4 (triangles) S2 (circles) and a gear and bearing oil (diamonds). In friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 40° C., and a pressure of 1.25 GPa, the friction coefficient is less than about 0.025. PAO4 and S2 were used at 67% treat in the blends. S2 outperforms the PAO4 blend despite slightly higher kinematic viscosity.

FIG. 11 graphically depicts friction coefficient over 0-100% slide-to-roll ratio (SRR) in MTM traction for bimodal blends of similar viscosity (˜460 cSt at 40° C.). The bimodal blends include PAO2 (squares), PAO4 (triangles) S2 (circles) and a gear and bearing oil (diamonds). In friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 100° C., and a pressure of 0.75 GPa, the friction coefficient is less than about 0.01. PAO4 and S2 were used at 67% treat in the blends. S2 outperforms the PAO4 blend despite slightly higher kinematic viscosity.

FIG. 12 graphically depicts friction coefficient over 0-100% slide-to-roll ratio (SRR) in MTM traction for bimodal blends of similar viscosity (˜460 cSt at 40° C.). The bimodal blends include PAO2 (squares), PAO4 (triangles) S2 (circles) and a gear and bearing oil (diamonds). In friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 100° C., and a pressure of 1.25 GPa, the friction coefficient is less than about 0.02. PAO4 and S2 were used at 67% treat in the blends. S2 outperforms the PAO4 blend despite slightly higher kinematic viscosity.

FIG. 13 graphically depicts the effect of gradual addition of liquid crystal S2 into 4 cSt PAO on friction reduction over 0-100% slide-to-roll ratio (SRR) at fixed pressure of 0.75 GPa and various temperatures from 40° C. to 140° C. Gradual reduction of traction coefficient is clearly associated with the increase of liquid crystal S2 concentration.

FIG. 14 graphically depicts the effect of gradual addition of liquid crystal S2 into 4 cSt PAO on friction reduction over 0-100% slide-to-roll ratio (SRR) at fixed temperature of 80° C. and various pressures from 0.75 GPa to 1.25 GPa. Gradual reduction of traction coefficient is clearly associated with the increase of liquid crystal S2 concentration.

PCT and EP Clauses:

1. A lubricating oil base stock comprising one or more liquid crystals, wherein the one or more liquid crystals are represented by the formula:

R1-(A)_(m)-Y—(B)_(n)—R2

wherein R1 and R2 are the same or different and are a substituted or unsubstituted, hydrocarbon, alkoxy or alkylthio group having from 2 to 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH2-CH2-, —CH═CH—, —OCOO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO2-, —CH2O—, —OCH2O—, —NO—, —ONO2, or —C≡N; and m and n are independently 0, 1, 2 or 3; and wherein the lubricating oil base stock has a kinematic viscosity of 2 cSt to 200 cSt at 40° C., as determined according to ASTM D445, and a kinematic viscosity of 1 cSt to 25 cSt at 100° C., as determined according to ASTM D445.

2. The lubricating oil base stock of clause 1 wherein, in friction coefficient measurements of the lubricating oil base stock by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 100° C., and a pressure of 1 GPa, the friction coefficient is less than 0.02.

3. The lubricating oil base stock of clause 1 wherein, in friction coefficient measurements of the lubricating oil base stock by a mini-traction machine (MTM) at a 30% slide-to-roll ratio (SRR), a temperature of 80° C., and over a pressure of 0.6-1.4 GPa, the friction coefficient is less than 0.02.

4. The lubricating oil base stock of clause 1 wherein, in friction coefficient measurements of the lubricating oil base stock by a mini-traction machine (MTM) at a 30% slide-to-roll ratio (SRR), a pressure of 1 GPa, and over a temperature of 0° C.-150° C., the friction coefficient is less than 0.025.

5. The lubricating oil base stock of clause 1 wherein, in elastohydrodynamic lubrication (EHL) film measurements of the lubricating oil base stock over a 10-1000 mm/s rolling speed using a mini-traction machine (MTM), at a temperature of 40° C. or 100° C., the EHL film thickness is greater than 8 nm.

6. The lubricating oil base stock of clauses 1-5 wherein the one or more liquid crystals are represented by the formula:

7. The lubricating oil base stock of clauses 1-5 wherein the one or more liquid crystals are selected from the group consisting of 4′-n-octyl-4-cyano-biphenyl, 4-(trans-4-heptylcyclohexyl)-pentylbenzene, 4-(trans-4-heptylcyclohexyl)-propylbenzene, and 4-(trans-4-propylcyclohexyl)-ethylbenzene.

8. The lubricating oil base stock of clauses 1-7 further comprising one or more viscosity modifiers to form a bimodal blend.

9. A method for improving wear control, while maintaining or improving energy efficiency, in an engine or other mechanical component lubricated with a lubricating oil, by using as the lubricating oil a formulated oil, said formulated oil having a composition comprising at least one lubricating oil base stock; wherein the at least one lubricating oil base stock comprises one or more liquid crystals, wherein the one or more liquid crystals are represented by the formula:

R1-(A)_(m)-Y—(B)_(n)—R2

wherein R1 and R2 are the same or different and are a substituted or unsubstituted, hydrocarbon, alkoxy, or alkylthio group having from 2 to 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH2-CH2-, —CH═CH—, —OCOO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO2-, —CH2O—, —OCH2O—, —NO—, —ONO2, or —C≡N; and m and n are independently 0, 1, 2 or 3; and wherein the lubricating oil base stock has a kinematic viscosity of 2 cSt to 200 cSt at 40° C., as determined according to ASTM D445, and a kinematic viscosity of 1 cSt to 25 cSt at 100° C., as determined according to ASTM D445; and wherein wear control is improved and to energy efficiency is maintained or improved as compared to wear control and energy efficiency achieved using a lubricating oil containing a lubricating oil base stock other than the lubricating oil base stock comprising one or more liquid crystals.

10. The method of clause 9 wherein, in friction coefficient measurements of the lubricating oil base stock by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 100° C., and a pressure of 1 GPa, the friction coefficient is less than 0.02.

11. The method of clause 9 wherein, in friction coefficient measurements of the lubricating oil base stock by a mini-traction machine (MTM) at a 30% slide-to-roll ratio (SRR), a temperature of 80° C., and over a pressure of 0.6-1.4 GPa, the friction coefficient is less than The detergent concentration in the lubricating oils of this disclosure can range from about 0.5 to about 6.0 weight percent, preferably about 0.6 to 5.0 weight percent, and more preferably from about 0.8 weight percent to about 4.0 weight percent, based on the total weight of the lubricating oil.

12. The method of clause 9 wherein, in friction coefficient measurements of the lubricating oil base stock by a mini-traction machine (MTM) at a 30% slide-to-roll ratio (SRR), a pressure of 1 GPa, and over a temperature of 0° C.-150° C., the friction coefficient is less than 0.025.

13. The method of clause 9 wherein, in elastohydrodynamic lubrication (EHL) film measurements of the lubricating oil base stock over a 10-1000 mm/s rolling speed using a mini-traction machine (MTM), at a temperature of 40° C. or 100° C., the EHL film thickness is greater than 8 nm.

14. The method of clauses 9-13 wherein the one or more liquid crystals are represented by the formula:

15. The method of clauses 9-13 wherein the one or more liquid crystals are selected from the group consisting of 4′-n-octyl-4-cyano-biphenyl, 4-(trans-4-heptylcyclohexyl)-pentylbenzene, 4-(trans-4-heptylcyclohexyl)-propylbenzene, and 4-(trans-4-propylcyclohexyl)-ethylbenzene.

All patents and patent applications, test procedures (such as ASTM methods, UL methods, and the like), and other documents cited herein are fully incorporated by reference to the extent such disclosure is not inconsistent with this disclosure and for all jurisdictions in which such incorporation is permitted.

When numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated. While the illustrative embodiments of the disclosure have been described with particularity, it will be understood that various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the spirit and scope of the disclosure. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the examples and descriptions set forth herein but rather that the claims be construed as encompassing all the features of patentable novelty which reside in the present disclosure, including all features which would be treated as equivalents thereof by those skilled in the art to which the disclosure pertains.

The present disclosure has been described above with reference to numerous embodiments and specific examples. Many variations will suggest themselves to those skilled in this art in light of the above detailed description. All such obvious variations are within the full intended scope of the appended claims. 

1. A lubricating oil base stock comprising one or more liquid crystals, wherein the one or more liquid crystals are represented by the formula: R1-(A)_(m)-Y—(B)_(n)—R2 wherein R1 and R2 are the same or different and are a substituted or unsubstituted, hydrocarbon, alkoxy, or alkylthio group having from about 2 to about 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH2-CH2-, —CH═CH—, —OCOO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO2-, —CH2O—, —OCH2O—, —NO—, —ONO2, or —C≡N; and m and n are independently 0, 1, 2 or 3; and wherein the lubricating oil base stock has a kinematic viscosity of about 2 cSt to about 200 cSt at 40° C., as determined according to ASTM D445, and a kinematic viscosity of about 1 cSt to about 25 cSt at 100° C., as determined according to ASTM D445.
 2. The lubricating oil base stock of claim 1 wherein, in friction coefficient measurements of the lubricating oil base stock by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 100° C., and a pressure of 1 GPa, the friction coefficient is less than about 0.02.
 3. The lubricating oil base stock of claim 1 wherein, in friction coefficient measurements of the lubricating oil base stock by a mini-traction machine (MTM) at a 30% slide-to-roll ratio (SRR), a temperature of 80° C., and over a pressure of 0.6-1.4 GPa, the friction coefficient is less than about 0.02.
 4. The lubricating oil base stock of claim 1 wherein, in friction coefficient measurements of the lubricating oil base stock by a mini-traction machine (MTM) at a 30% slide-to-roll ratio (SRR), a pressure of 1 GPa, and over a temperature of 0° C. to 150° C., the friction coefficient is less than about 0.025.
 5. The lubricating oil base stock of claim 1 wherein, in elastohydrodynamic lubrication (EHL) film measurements of the lubricating oil base stock over a 10-1000 mm/s rolling speed using a mini-traction machine (MTM), at a temperature of 40° C. or 100° C., the EHL film thickness is greater than about 8 nm.
 6. The lubricating oil base stock of claim 1 wherein the one or more liquid crystals are represented by the formula:


7. The lubricating oil base stock of claim 1 wherein the one or more liquid crystals are selected from the group consisting of 4′-n-octyl-4-cyano-biphenyl, 4-(trans-4-heptylcyclohexyl)-pentylbenzene, 4-(trans-4-heptylcyclohexyl)-propylbenzene, and 4-(trans-4-propylcyclohexyl)-ethylbenzene.
 8. The lubricating oil base stock of claim 1 further comprising one or more viscosity modifiers to form a bimodal blend.
 9. The lubricating oil base stock of claim 8 wherein, in friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 40° C., and a pressure of 0.75 GPa, the friction coefficient is less than about 0.02.
 10. The lubricating oil base stock of claim 8 wherein, in friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 40° C., and a pressure of 1.25 GPa, the friction coefficient is less than about 0.025.
 11. The lubricating oil base stock of claim 8 wherein, in friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 100° C., and a pressure of 0.75 GPa, the friction coefficient is less than about 0.01.
 12. The lubricating oil base stock of claim 8 wherein, in friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 100° C., and a pressure of 1.25 GPa, the friction coefficient is less than about 0.02.
 13. The lubricating oil base stock of claim 8 wherein the viscosity modifier comprises a polymer thickening agent comprising a co-oligomer of 1-propylene and ethylene.
 14. A method for improving wear control, while maintaining or improving energy efficiency, in an engine or other mechanical component lubricated with a lubricating oil, by using as the lubricating oil a formulated oil, said formulated oil having a composition comprising at least one lubricating oil base stock; wherein the at least one lubricating oil base stock comprises one or more liquid crystals, wherein the one or more liquid crystals are represented by the formula: R1-(A)_(m)-Y—(B)_(n)—R2 wherein R1 and R2 are the same or different and are a substituted or unsubstituted, hydrocarbon, alkoxy, or alkylthio group having from about 2 to about 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH2-CH2-, —CH═CH—, —OCOO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO2-, —CH2O—, —OCH2O—, —NO—, —ONO2, or —C≡N; and m and n are independently 0, 1, 2 or 3; and wherein the lubricating oil base stock has a kinematic viscosity of about 2 cSt to about 200 cSt at 40° C., as determined according to ASTM D445, and a kinematic viscosity of about 1 cSt to about 25 cSt at 100° C., as determined according to ASTM D445; and wherein wear control is improved and energy efficiency is maintained or improved as compared to wear control and energy efficiency achieved using a lubricating oil containing a lubricating oil base stock other than the lubricating oil base stock comprising one or more liquid crystals.
 15. The method of claim 14 wherein, in friction coefficient measurements of the lubricating oil base stock by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 100° C., and a pressure of 1 GPa, the friction coefficient is less than about 0.02.
 16. The method of claim 14 wherein, in friction coefficient measurements of the lubricating oil base stock by a mini-traction machine (MTM) at a 30% slide-to-roll ratio (SRR), a temperature of 80° C., and over a pressure of 0.6-1.4 GPa, the friction coefficient is less than about 0.02.
 17. The method of claim 14 wherein, in friction coefficient measurements of the lubricating oil base stock by a mini-traction machine (MTM) at a 30% slide-to-roll ratio (SRR), a pressure of 1 GPa, and over a temperature of 0° C.-150° C., the friction coefficient is less than about 0.025.
 18. The method of claim 14 wherein, in elastohydrodynamic lubrication (EHL) film measurements of the lubricating oil base stock over a 10-1000 mm/s rolling speed using a mini-traction machine (MTM), at a temperature of 40° C. or 100° C., the EHL film thickness is greater than about 8 nm.
 19. The method of claim 14 wherein the one or more liquid crystals are represented by the formula:


20. The method of claim 14 wherein the one or more liquid crystals are selected from the group consisting of 4′-n-octyl-4-cyano-biphenyl, 4-(trans-4-heptylcyclohexyl)-pentylbenzene, 4-(trans-4-heptylcyclohexyl)-propylbenzene, and 4-(trans-4-propylcyclohexyl)-ethylbenzene.
 21. The method of claim 14 wherein the lubricating oil comprises a bimodal blend of the at least one lubricating oil base stock comprising the one or more liquid crystals, and one or more viscosity modifiers.
 22. The method of claim 21 wherein, in friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 40° C., and a pressure of 0.75 GPa, the friction coefficient is less than about 0.02.
 23. The method of claim 21 wherein, in friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 40° C., and a pressure of 1.25 GPa, the friction coefficient is less than about 0.025.
 24. The method of claim 21 wherein, in friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 100° C., and a pressure of 0.75 GPa, the friction coefficient is less than about 0.01.
 25. The method of claim 21 wherein, in friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 100° C., and a pressure of 1.25 GPa, the friction coefficient is less than about 0.02.
 26. The method of claim 21 wherein the viscosity modifier comprises a polymer thickening agent comprising a co-oligomer of 1-propylene and ethylene.
 27. The method of claim 14 wherein the lubricating oil further comprises one or more of an antiwear additive, viscosity modifier, antioxidant, detergent, dispersant, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, anti-foam agent, inhibitor, or anti-rust additive.
 28. The method of claim 14 wherein the lubricating oil is a passenger vehicle engine oil (PVEO). 